All Along the Crooked Way - An Assassin's Handbook

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All Along The Crooked Way - An Assassin's Handbook

"It's done. You've sold a part of your soul to the Shadow and taken its mark" the shadow creatures said.

"What will come now?" asked the assassin, still trembling after the ritual.

"It's up to you". "The Path of Shadow is a lonely one". The shadow creatures departed and left the assassin alone.
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Can we leave our hero to its destiny? Of course, not! So we'll help him with a little advice about what he should do.

Selling Points - Reasons to sell your soul to shadow

High mobility: with a lot of teleport powers including an-at will the assassin is one of the most mobile classes.
Flexibility: there are a lot of different builds as the striker and the controller roles in the assassin have an almost equal value.
Spike Damage: you'll never be a whirling monster-slicer as the Ranger, but you can do pretty serious spike damage and build it up from a safe distance.
A different approach to survival: with controller hit-points and surges, you will have to change your mind about how to survive  and change your strategy continuously. It can be quite refreshing and new for anybody used to defenders who trade hits with monsters.


We'll use "LBD's standard colour coding" (TM) for this handbook as it fits well our purposes but with the "green variant" using black only to generally highlight some text:
Red: Garbage, or completely overshadowed by another option.
Purple: Situationally useful, but overall pretty meh.
Green: OK. You could do worse than pick this.
Blue: Good stuff. You probably want this.
Sky Blue: You want this. Period.
Gold: Why haven't you taken this yet? A defining choice for a build, or even the whole class.

We will also show rating differences based on the Guilds whenever needed.

This Handbook covers the following sources:
AP - Arcane Power
AV - Adventurer's Vault
AV 2 - Adventurer's Vault 2
D XXX - Dragon Magazine, issue XXX
DMA 2009 - Dragon Magazine Annual 2009
DP - Divine Power
EPG - Eberron Player's Guide
FRPG - Forgotten Realms Player's Guide
MM - Monster Manual
MM 2 - Monster Manual 2
MOTP - Manual of the Planes
MP - Martial Power
MP2 - Martial Power 2
PHB - Player's Handbook
PHB 2 - Player's Handbook 2
PHB 3 - Player's Handbook 3 (what we have so far)
PHH 1 - Player's Handbook Heroes: Series 1
PHH 2 - Player's Handbook Heroes: Series 2
PP - Primal Power

I will mainly use the Compendium as a source so I may be a little out-of date on the Dragon Magazine's side from time to time.

Thanks to:
Armisael for the picture of Agent 47 - now I moved to Anomander Rake
LDB for reviving the debate about the assassin
Chanter Hound for his Assassin Handbook
Psk20, DoctoBadWolf, Awesomologist, Ozovio, HidaKenshiro, Sn0wm4n, AfossDDI e Squad for constant support, suggestion and for finding my mistakes around.
All those who will post.

Getting started

Baseline mechanics (HP, Surges and proficiencies):

Hit points: 10+ constitution at first level, 4 for each level afterwards. This is as low as you can get and will condition your entire career and development. Never forget that.
Surges: 6 + Con modifier. Once again it's the minimum.
Armor proficiences: cloth and leather are what you get, but honestly you couldn't expect more. Assassins in plate armor are not popular. You are proficient in light shields and using one can be a good idea for a build based on Implement powers.
Weapon proficiences: you get a solid array for you purposes. If you want to use Weapon powers you'll probably look for an exotic weapon though (Fullblade or Executioner's axe).
Implements: ki foci and weapons are a pretty good array. The fact that you can seamlessly switch from one to the other and use your ki focus with any weapon is even better. The main limit at the moment is the limited list of ki foci, but PHB3 should fix this.

Features:

Assassin's Shroud: your baseline striker mechanic. From a surface scan it seems good due to damage on a miss and the chance to safely build it up from a distance, but a deeper analysis shows that it scales poorly with the tiers and cannot be fully exploited in many cases due to your target dying before you can invoke the shrouds.
The best recommendations for use are probably:

• Avoid the main target of the party attacks, unless it's a solo or it's the only real threat of the encounter. It will die fast if fire is concentrated.


• Use it on low hp isolated targets like controllers or artillery behind enemy lines as long as your allies are not peppering them with ranged/area attacks. This allows you to build up shrouds and use them in a single burst to deal huge damage compared to target's hp. If you kill them outright you'll take out a source of damage/status effects for the rest of the encounter.


• If you can't point out a good target, invoking every time you have two shrouds on the target will give you a reasonable damage output with a relatively low risk of losing shrouds due to the target's death.

Shade form: it's a good power for scouting and good also if you find yourself in a difficult situation (i.e. ganged-up by monsters). The main drawback is that it is often difficult to judge when to use it.
If you take the Assassin's Escape feat then this feature becomes blue as you can use it as an immediate interrupt (halving crit damage can save your life).

Shadow Step: an at-will teleport is simply fantastic. The range is not long and you have some conditions but then again it's an at-will teleport from level 1. You can automatically escape grabs, partially avoid the immobilized condition and very often avoid opportunity attacks.

Guild training will be treated in another post as it shapes your strategies.

Skills

Stealth: you get it for free. With Shade Form and the amazing number of powers that make you invisible, you'll get a lot out of stealth. Some Bleak Disciple "Tough Guy" builds may not need it but for most assassins it's the main skill.

Assassin Skills:

Acrobatics: it's dex based so you'll have a good score if you want to pull stunts or reduce fall damage. One of the main points (escaping a grab) is almost useless for you as you can usually teleport out.

Arcana: so far intelligence is a dump-stat and Arcana is not really useful in any way. This may change if the third assassin build will have Int as a secondary.

Athletics: unless you want to do a lot of climbing or swimming I don't see much here.

Bluff: useful for hiding when you don't have other ways to do that. This rating is for Nightstalkers, for Bleak Disciples it's probably purple.
Endurance: resisting disease and holding your breath are the main targets. This rating is for Bleak Disciples who have Con as secondary. For Nightstalkers it's purple. A side note for Revenant Assassins. There's a feat called Death's Blessing that makes you undead. If you plan to take that then endurance is purple for you in any case.

Insight: it keys off wisdom, which may be your tertiary ability for some builds. Anyway it's likely that somebody else in the group will be better that you at this.

Perception: I know it's Wisdom based, but for your job it's quite important. If you plan to scout ahead of the group while hidden and build up shrouds from a safe place before launching the first attack, you'd better be able to detect dangers. A single trap that alerts monsters can spell doom for you.

Streetwise: I won't rate this, as it really depends on how your DM plays. It's clearly better for Nightstalkers.

Thievery: you're good at it. Combined with Stealth and Perception forms the core of the archetypal assassin.

Ability Scores

Strenght: for some builds it can be the tertiary score. It helps if you are a Bleak Disciple and aim for Hide Armor Proficiency or a Nightstalker to increase your Fortitude. It may also help for Soul Thief builds who plan to multiclass in order to take Barbarian encounter multiattack powers like Storm of Blades or Hurricane of Blades.
Recommended starting score: 10-12 before racials.

Constitution: constitution is the secondary ability for Bleak Disciples but is also useful for Nightstalkers to offset the low hp/surges.
Recommended starting score: 12-16 before racials.

Dexterity: it's the main stat, to be boosted whenever a chance is offered. Recommended starting score: 16-18 before racials

Intelligence: so far it's a dump-stat. Recommended starting score: 8-10 before racials

Wisdom: a reasonable score here can improve your Perception. Also useful if you want to multiclass into avenger or cleric. It also helps Bleak disciples on the Will side and they may prefer it to Charisma, unless they want to take powers with a Cha-based rider. Recommended starting score: 10-12 before racials.

Charisma: it's the secondary ability for Nightstalkers. For Bleak Disciples it's not that helpful so they can have a lower score here. Recommended starting score: 14-16 for Nightstalkers, 10-12 for Bleak Disciples before racials.

Races

PHB1:

Dragonborn: this race got a boost with the Emerald Scale Concealment feat. Bonus to Cha is ok but you'll probably have to start with an 18 in Dex.
Dwarf: nothing special here. Using second wind as a minor is not bad but resilience is all you have. Better go revenant/dwarven past.Eladrin: bonus to Dex and an extra teleport per encounter for more mobility. And a lot of feat support for Fey Step. Not the best choice around but not the worst either.Elf: bonus to Dex and Wis (primary and tertiary abilities), 1 square more of movement and a reroll power. An extra bonus to Perception. The Dusk Elf line of feats offers even more support.Half-Elf: after the nerfing of Velvet Blade Trick it's an average choice. You get a bonus to a secondary ability and Dilettante.
Halfling: you will most likely take Nightstalker. The extra damage from the Feature can easily make you outdamage Medium-sized Bleak Disciples when you use weapons, and implements will work absolutely fine. Bonuses on both main abilities, a defensive reroll power. The rating is basing on taking Nightstalker, as you won't look into the Bleak Disciple guild.
Human: as usual humans are a good choice. +2 to Dex, +1 to NADs and 1 extra feat. The extra feat is the cherry on top: most assassin builds tend to be a little feat starved and one more is a great boon.Tiefling: similar to the half-elf, with a bonus to a secondary ability. Good skills bonuses (Bluff and Stealth) and an interesting racial

PHB2:
Deva: bonuses to your dump-stat (Int) and Wis. The racial power is the only plus, but overall you'd better go looking elsewhere.Gnome: bonus to Cha and fading racial power are the upside, small size, speed 5 and a bonus to Int go the other way. An average choice for a Nightstalker, don't touch it if you want to be a Bleak Disciple.
Goliath: a dark blue choice for a Bleak Disciple. Bonus to Con, a very good racial power (Stone's Endurance and Shade Form together can negate a lot of damage for one round), Goliath Greatweapon Prowess and feats that upgrade your racial power.
Half-orc: interesting for both Guilds. Bleak Disciple can find another source of THP (Half-Orc Resilience) improvable by feats and an easy access to Hide Armor Proficiency. But also Nightstalker will benefit for THP with their low HP pool. Shifter, Razorclaw: like an elf more or less, with interesting feats based on the racial power triggering. The problem is that the power triggers when you go bloodied. Depending on your party make this can happen often or rarely. Blue seems appropriate.
Shifter, Longtooth: two bad stat bonuses and a racial power that has the same issue of the Razorclaw. All in all a sub-par choice.

PHB3:
Githzerai: A Dex/Wis bonus race like the elf. Nice bonuses (+2 to initiative and several saves), Iron Mind as a defensive racial and interesting feats (Githzerai Blade Master is pretty famous and the new Dakhshai's Body Mind Union and Miryath's first strike are quite suitable for assassins)
Wilden: a bonus to the secondary (Con) and tertiary ability (Wis) for a Bleak Disciple and nice racial power. Feat support is not very good though.

MM1:
Bugbear: quite some potential here. Dex bonus, Stealth bonus, Oversized for bigger weapons, and a damaging racial. Can pull quite some damage from first level with 4 shrouds+predatory eye (5d6 extra) once per encounter. The limit is that we don't have any feat support.
Githyanki: Con bonus is ok for Bleak Disciples and the bonus to initiative always helps. But there it ends. Better go to the other side of the gith universe.
Goblin: very similar to the halfling, so suitable for Nightstalkers, even if small. Take a bastard sword two-handed or implement powers and it should work. The rating is based on taking the Nightstalker's Guild Training, as the other is not very interesting for a goblin, and is lower than that of the halfling mainly for the lack of feat support.
Hobgoblin: bonus to Cha and Con and a nice racial power. No feat support though. 
Kobold: an undecided race. The bonus to Con would be better for Bleak Disciples, but you'd like to be a Nightstalker because you're already small. Shifting as a minor is always useful even when you can teleport. No feat support so far, but the bonus to Dex is always good for an assassin.
Orc: a good racial power and bonus to Con. You can do a reasonable Bleak Disciple but no feat support leaves you a bit behind.
MM2:
Bullywug: even if stat bonuses would be ok, you have a terrible racial (no many monsters spend healing surges) and no feat bonuses.
Duergar: green for Bleak Disciples. Bonus to Con and Wis and a nice racial power, but no feat support. The racial power combines well with the Venomed Soul PP. You can use Infernal Quills to deal ongoing poison damage to your target with a minor action and then follow with an action point to enjoy a nice +Con bonus to attack rolls until the end of your next turn.
Kenku: the basis is outstanding for a Nightstalker. Bonuses to Dex and Cha, bonus to Stealth, +3 instead of +2 to attack when flanking. Blue until some feat support comes, but very close to sky blue.

FRPG:
Drow: drow are the archetypal Nightstalkers. They are even mentioned in the Guild description as the source of this kind of training. Bonus to Dex and Cha, darkvision, cloud of darkness and a good feat list. Genasi: almost nothing useful. 
EPG:
Changeling: an outstanding choice for a Nightstalker. Bonus to Dex and Cha, changeling disguise and a minor action bluff to get CA once per encounter. Blue until more feat support will be available.Kalashtar: the ability bonuses are not that bad, but the chance of you racial power triggering is low. At higher level attacks against Will are more common, but I feel than in many encounters there will not be any chance to activate the racial power. And since most of the feat support is linked to it...Warforged: maybe it can be a green choice for a Bleak Disciple. Great resilience comes from both the racial power and many feats. If somebody could look into a build it would be my pleasure to post it here.

Dragon Magazine:
Gnoll: great for any build, though Con bonus points towards Bleak Disciple. Speed 7, bonus to Perception and a great racial power than can be improved with feats like Maw of the Hungry Killer and those who let you use an at-will or encounter power at the end of the charge. Bonuses to damage when you're bloodied and when you fight a surrounded enemy are icing on the cake.
Minotaur: I was thinking of giving it a green rating for a Bleak Disciple, but it doesn't make the cut. The main problem is that the racial power is Strength based and some interesting feat support is exactly there.
Revenant: this race was designed to fit the Assassin's class. You get a bonus to Dex and Con, Unnatural Vitality that reduces your squishiness and can be abused to an extreme level, a good racial feat list and access to the feats of your past race. Depending on your build you may look for different past lifes. A few examples (this is an assassin's handbook not a revenant's)

- Bladeling: take Past Soul and Improved Razor Storm to get a minor encounter close burst 2 attack as a minor, Dex based for damage and ongoing damage. Works wonders with Well of Shades and opens the way for quite a nice combo (Well of Shades+Spectral Assailants+Improved Razor Storm and then teleport out).
- Half-elf for Dilettante and later Versatile Master
- Dwarf for more toughness (Shaka's build called Mrs. Tough Guy shows this more than mere words)
- Githzerai to take Githzerai Blade Master
- Shadar-Kai to aim for the Raven Consort Epic Destiny (the Undying assassin build)
- Human for feats like Action Surge (to increase your chance of hitting with dailies/encounters) and possibly the Adroit Explorer PP.
The racial PP Avenging Haunt is also interesting if you really want to go for an unkillable character.

Shadar-kai: the bonus to Int is a waste but everything else is good. Shadow jaunt gives you an unrestricted teleport and insubstantiality for one round. At epic, Deathless Warrior is a great feat for an assassin and Raven Consort is a great ED.

Guild training

Deciding your guild training is one of the most important moments in creating your assassin. As both trainings will give you a substantial bonus in one area you will most likely optimize your feats and powers in order to exploit that bonus. Let's look at them in detail.

Bleak Disciple:

Show

Bleak Disciple: when you hit an un-bloodied target you gain THP equal to your Con mod. This scales at 2+Con mod at paragon and 4+Con mod at epic.

This is probably the best THP generating mechanic within 4ed. If you can choose your targets wisely you will get a constant flow of THP that mitigates your squishiness. On the other hand you'll go for a lower DPR than Nightstalkers. As your damage will be lower you should try to look for bigger weapons (Fullblade and Executioner's axe for example) to increase your DPR a little and on the other hand you should try to outlast your enemies by improving your ability to take punishment, because you will need more time to wear down your enemies. You'll probably tend to gravitate more towards weapon encounter powers as you can afford to stay toe-to-toe with most monsters and because most of the powers who have a rider for Bleak Disciples are weapon based (Well of Shades being the only exception, and a notable one). By the way, all the powers with a Guild-based rider are encounter attack ones. No daily, at-will or utility is influenced by your guild training. 

Nightstalker:

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Nightstalker: you add your Cha to damage you inflict to any target who is not adjacent to any of your enemies. This is clearly a good boost to damage and your DPR will be higher than that of a Bleak Disciple. Unfortunately you're even more fragile than a glass cannon. To properly play a Nightstalker and survive you'll most likely need one or more of these factors:
- a party that can protect you. If you have a solid front line of defenders who let you use implement powers from behind the line, then you have a better survival chance. Melee brutes are the main risk for you as they can deal high damage in one shot.
- a choice of powers that let you become invisible/insubstantial/let you hide consistantly over the course of an encounter
- one or more sources of damage reduction, like a Rain of Hammers Ki Focus or similar equipment.
Your business is attacking isolated enemies so powers that let you isolate enemies are good (Executioner's hood to pull them in a favourable position, powers that let you teleport the target).
Looking at the powers with a rider based on your Guild, there are 5 implement based ones and 2 weapon based. Many of them have either the Fear keyword, or the Psychic one or both. 

Heroic Tier Powers

1st level at-will powers:

Executioner's noose: all in all superior to Inescapable Blade. Range is better, damage is similar or better as you add your Dex bonus, you can pull and slow for added control. Nightstalker could find it useful to move the target into an isolated position. Works well also with the Wall powers (Wall of Shadows, Wall of Death).

Inescapable Blade: the only advantage over Executioner's Noose is that you ignore cover and superior cover. In my games this is unfrequent, but depending on your DM's style it can be an interesting point.

Leaping shade: it encourages you in not invoking your shrouds. I can't see why you shouldn't take Shadow storm over it every time. Even with four shrouds you will get +4 to damage a round if you hit, against 3,5 (shroud) + at least 1 for Shadow Storm.

Shadow Storm: there is no reason not to take it. It constantly gives you at least +1 to damage (as you are a creature) and can go up to very high numbers in a crowded encounter. By far the best at-will for Bleak Disciples. If you're a Nightstalker try to make sure not to be adjacent to too many enemies at end of your turn.


1st level encounter powers:
Gloom thief: the typical 2[W] first level encounter but with a very good side effect like invisibility until the end of yor next turn if you're within 2 squares of the target. Remember that you become visible if the target moves away from you, so a defender who can avoid it moving will always be helpful.

Nightmare Shades: combat advantage + Cha bonus to damage until the end of your next turn for Nightstalkers. Green for Bleak Disciples who don't get the bonus to damage.

Shadow Darts: one of the best powers to ensure that your shrouds do not go wasted. Good chance to crit and maximize shroud damage. Anyway see below.

Smothering Shadow: for Bleak Disciples, green for Nightstalkers who do not get the extra damage.

All in all the first level encounter powers are well leveled. 3 are good for Nightstalkers and 3 for Bleak Disciples.
Doing a deep calculation for 1st level characters with the following assumptions:
Weapon: great sword (+3 prof)
Dex Bonus: +4   Con bonus Bleak Disciple:+4    Cha bonus Nightstalker: +4
AC target: 15    Other defenses target: 13
No other bonuses. 1 to 4 shrouds.
We get the results that Shadow Darts and Gloom Thief do almost exactly the same damage, Nightmare Shades does about 1 point more (if no action points are used), Smothering Shadow up to another 2,5 more. Shadow darts would probably get on par with Nightmare Shades as soon as +1 implement is used. I hope my math is ok.

1st level daily powers:
Grave Spike:  nice damage, knocks prone and ongoing 5 damage (save ends). And +2 to hit the target until the end of the encounter.

Strangling Shadow: less damage than Grave Spike and no effect until the end of the encounter.
Even if it attacks Fort it's green for me. You can maybe use the pull to bring the target into the ranks of your party to better exploit Shadow Storm afterwards. This can be a double-edged trick if the target has burst powers as you'll fetch targets for him.

Targeted for Death: good damage, attacks will and has a fantastic rider that doubles your shrouding power on the target until the end of the encounter.

Terrifying Visage: similar to Strangling Shadow as it immobilizes the target. The damage will be always lower than Strangling Shadow, (as 1[w]+5 will be usually higher than 2d8 and this if the target makes the first save against Grave Spike's ongoing damage). You get to push secondary targets to isolate the first one. This shoul supposedly be good for Nightstalker but you lack the ability to keep them away.

As a side note, remember that many assassin daily powers have a rider that lasts until the end of the encounter on a target. Not to waste your daily you should choose your target wisely. Goggles of Aura Sight can be an interesting object for you. A minor action and you know if it makes sense to land a daily on that creature or not.


2nd level utilities:
Cat's Trickery: nothing special. Very often light sources will be multiple and by the way the duration is short. It could be interesting in a defensive way if you don't have darkvision and are attacked by a creature that brings darkness on you. All in all purple seems ok.

Cloak of Shades: a good power. Synergizes well with Shade Form too. Especially good in avoinding being peppered by enemy artillery/controllers with ranged powers.

Contrivance of Speed: for straight assassins this power is pretty poor. It is mainly useful if you fight an isolated target, as you have Shadow Step to use in crowded fights. I see it more useful for Assassin/Avenger hybrids who maybe do not have Shadow Step (no surprise this power appeared in the Covenant Agent article on Dragon). 

Converging Shadows: nothing special here. Concealment is fine but duration is short and you can make a stealth check only if you're missed. It's an encounter so a little better for that.

Distracting Illusion: if you have Hidden Insight you can get some free rounds to build up shrouds.  Better for Nightstalker who can pile their Cha bonus on the Bluff check. Open also some interesting role-playing opportunities but that depends a bit on your DM too. 

 Endure Pain (Endurance Skill): an interesting utility with damage resistance, but it's a daily.

Inspiring Fortitude (Endurance Skill): blue for Bleak Disciples. At low levels you can dish out a huge amount of THP compared to the HP pool of the party and still solid going up in levels. Less useful for Nightstalkers. 

Lurking shadow: it could be a very good sneaking utility, but it ends if you enter a bright light square and it's a daily. In dim-lighted dungeons can be useful to do some scouting.

Shadowed Legion: it doesn't make sense to rate this power in a vacuum. It's usefulness totally depends on the make up of your party. If your allies are a bunch of metal clankers than can be heard at miles of distance then it can be at least blue. If they are stealthy guys then it can be better to look elsewhere.

Silent Stalker: good for scouting but considering that you're quite fragile I won't rate it high.

Summon the Mists: the area is good and it will help you in getting concealment but it offers the same benefit to your enemies and is a daily. 

Fast Hands (Thievery skill): a pretty good power to retrieve objects. It can be exploited by Revenant with the Death's quickening feat. When you drop below 0 HP, free action to draw a potion, minor to drink it and then resume bashing monsters on the head.



3rd level encounter powers:
Army of the night:  maybe blue for nightstalkers. This power can be nice or it can be not. If your master avoids moving enemies close to the target due to this power's effect, then the only real benefit is that you keep the target isolated (which is good only for nightstalkers). In that case, anyway, damage is a bit on the low side. 

Cloaking mist: if you can catch at least two targets in the blast the damage is absolutely nice. You can then hide with concealment only (e.g. activating Shade Form). It can be an interesting power if you intend to take the Soul Thief PP. You can recharge your soul shards by targeting (and hopefully killing) minions with this power. Be careful as this is party unfriendly blast.

Inescapable Shadow: nothing special for a 3rd level encounter. The teleport is ok. Normally it will only save you a move action.
Nightshades's kiss: damage is ok, but the control function is the main issue here, as you can move the target every time it is hit. An artificer ally with Barbed Automaton, or an Avenger with Threatening Strike can potentially set up very long loops of damage. With the right party build it can be sky-blue if you can exploit damage zones, walls and similar stuff.


5th level daily powers:
Heart of Dust: a good power. The base damage is ok and in a crowd it can really be deadly. The "area" damage is party-friendly as it only targets enemies. It's a poison power so if you have feats like Venom Hand Master at heroic or Venom Master (drow) at paragon or the Venom Soul PP , you'll be able to exploit it further. Be aware that against undead it wont'be effective unless you have Venom Hand Master.

Shadow Soul: it can situationally be useful against monsters able to turn invisible and hide but overall it's subpar. You have to hit in melee in first place, so the main reason to teleport is probably that the target is retreating and you don't want to follow him into the enemy ranks.

Treacherous Shades: damage is good and you can set-up some nice combat advantage. Enemies who were not hit or saved may think about moving away from their allies who did not, thus isolating some targets for Nightstalkers. But it's party unfriendly and even if sometimes your buddies can suck up some damage, I don't think they would like to grant combat advantage (save ends). This limits the use so green seems appropriate.
Twilight Assassin: your duplicate can help in a lot of ways. You can flank with it, you can use it to route enemies movement as it occupies one square and cannot be damaged. And it's a source of damage, attacking with a minor. Better use it early in the encounter.

Comparing Heart of Dust and Twilight Assassin, the first one will give you more damage immediately, while the other will build up over time as you assassin lands its hits.  



6th level utility powers:

Darkness: this one is terrible as it blocks line of sight for your allies too. In general I would avoid this kind of powers. It can be used to save you in case you're surrounded but you generally have better options.


Darting shadow: nice for doing some scouting around. Anyway you need a constant source of concealment/cover to stay hidden. Most likely this has to come from invisibility or darkness. Notable ways to exploit this power are paragon multiclassing into Warlock for the Walker in Gloom feat or at high levels using a Shadow Band. 

Ghost of the Rooftops: it may give you some opportunities out of combat (climbing especially), but in general you'll prefer to teleport whenever you can.

Slayer's Escape: this can save you from serious punishment if you get surrounded. You take the first hit, teleport and become invisible. And it's an encounter.
Shadow Adept: this is mainly useful if some enemy spots you, but honestly you could do better than this.

Sheltering Dark: another concealment/invisibility power. But not so appealing as the duration of invisibility is short and you have to move out of the area to activate it.

Slithering Shadow: the kobold stance (you can shift as a minor action). Usually you don't have much to do with your minor actions, but given the mobility you already have it's not a big boon as a daily.

Vanish: this is almost a clone of Slayer's Escape. Normally it will let you teleport a bit more as your speed should be more than 5, but it can backfire on you if you're slowed. 





7th level encounter powers:



Captured Shadow: you have to hit in melee and then you have a chance to teleport the target. Useful to reposition the target into a difficult position for him, if you move after hitting with Captured Shadow.

Echoing threat: green for a nightstalker, purple for a Bleak Disciple. If you choose your target wisely you'll most likely get the extra damage. Nightstalker get an extra teleport during the next round.

Shadow Jack: this is exactly the power every assassin wants. Damage is ok, you become insubstantial, if attacks miss you they hit your target (a good reason not to attack you), and you can enter from one square adjacent to the target and exit from another one, repositioning yourself.

Shadow Link: not the best power around. The THP rider for Bleak Disciples is relevant only if you hit a bloodied target, and the extra shroud when you are hit is not what you want (trading an hit for a shroud is not a good idea, better to soak up damage or avoid getting hit). Overshadowed by Shadow Jack.



9th level daily powers:



Black Garrote: it's a touch power, so you'll have lower chances to hit, but it's reliable. Inflicting 2d10+Dex automatically is good but you're not able to move freely and your target can always try to escape the grab thus ending the effect. Moreover you can't invoke shrouds or use any standard action (unless you use an AP). The best tactic is probably use this power and then activate Shade Form immediately. This combo is the only reason why I rate this green at least for Bleak Disciples who have high Fort and Ref defenses.

Bound by Shadow: in long fights this power can pile up a lot of damage but choosing the right target will not be easy. If for any reason the group concentrates on it, it will die before you can get any extra damage.

Obscuring shadow: damage is good and the effect is nice, but only the target cannot see you. Good against solos but they're bound to save soon.

Wall of Shadows: the fact that it blocks line of sight can be useful if you can cut the encounter in two areas, as it will force enemies to go across the wall or die under your ranged powers. If you can do this then the damage dealt will be massive. Even if you cannot do that, you can reroute enemies in a favourable way for your party. But this power has a serious drawback: it's party unfriendly. If you find monsters that can push/pull/slide, or dominate or frighten so that you run, then the wall can be used against your party by a grinning DM (never let the DM grin!!).

9th level dailies are somewhat a strange bunch. Each one as a lot of good things and drawbacks. Very difficult to rate.



10th level utilities:

Darkening Veil: it's a daily but quite good. First of all you basically get concealment until you sustain the power (as a minor) and you get to teleport for free if you're hit.

Death Mark: it may see use from time to time, and be very effective in that case (tracking a creature may really be saving your day), but I won't take it in general.

Eyes Unseen: you can use it to spy behind doors, walss and whatever. If you're mainly fighting in dungeons i would rate it blue or even sky blue, because you can use it to get knowledge of encounters in advance and plan accordingly.

Mist Walk: this would be interesting as en encounter. As a daily it's really underwhelming.

Promise of Retribution: a defensive power. It lets you teleport away and the back later in the encounter with some extra bonuses to attack and damage rolls. Not bad, but it's a daily.
Seeker of Shadow: extremely good for scouting but in a fight you're supposed to attack and hit, so it won't help much (and it's a daily). If you're working alone you can set-up a combo if you maximize your stealth and later take Assassin's Scalpel. You'll be able to slowly wear down any enemy by inflicting shroud damage only and hiding continuously. This is more a theoretical consideration as you'll need a lot of time to kill any monster.
Slayer's Endurance: amazing! This utility is the main reason around to take feats who let you put additional shrouds on a target. It can easily grant you 15-20 THP per encounter. For nightstalkers it's even better, but also Bleak Disciples will be able to take advantage of it. And it works also if you miss, as long as you inflict at least some shroud damage (i.e. as long as you have at least 2 shrouds on the target).

Vaporous Step: great mobility power. It will help you in slowly rearranging the battlefield. In a party of Slashers this power will turn the party into a meatgrinder...

Walk Through Shadow: I won't take it in general. Bypassing walls is bad if your buddies stay behind. And you already have teleporting abilities.

Paragon Tier Powers

13th level encounter powers:
Dark Step Ambush: Inescapable Shadow plus an invisibility rider. Not bad but you can do better at this level.



Flurry of Talons: another upgrade (in this case of Shadow Darts). Damage is solid and you can fly to the target, but it leaves you a little open to retaliation.



Slayer in the Dark: third upgrade (of Army of the Night this time). If your group can inflict some forced movement you can get some real damage of of this power, triggering some attacks. Otherwise you have to rely upon your master (as with Army of the Night). Probably green for a Bleak Disciple.


Spectral Assailants: at first glance it doesn't seem great, but it is. Actually it lets you one shot targets with the right setup. You can slide one square the target as fre action each time it takes damage until the end of you next turn. Combine it with a power like Lifedrinking Covenant (Avenger) to outright kill an enemy. Or with two damage zones for ping-pong deaths. You can slide the target even on its turn as it is a free action so teaming with you wizard ally using Cloud of Daggers works too, or your psion using Daggers of Pain. The only limit to one-shotting is DM fiat (i.e. limiting your free actions).
Well of Shades: a multi-target power and its a burst 3!! And you can then become invisible or teleport 5 and if you're a Bleak Disciple it also slows all the targets you hit. Fantastic on an AP with a Soul Thief. It's a nice set-up power for area/blast powers of your allies as it groups enemies. If you have the Lasting Frost feat you can make a nice combo with Well of Shades + Cloaking Mist. Later on you can set-up a different combo with Wall of Death. Downgraded to sky-blue only because of Spectral Assailants.


15th level daily powers:
Bleak Gallows: it can be an interesting power if you or your allies can place a damage zone near the gallows (and absolutely deadly if you have a Messenger of Peace in the group). The fact that the gallows appear close to the target doesn't help too much. It would have been much better to have the gallows appear adjacent to you. But the real problem is that the gallows only has 35 hp: 15th level monsters will wipe it out with two attacks. 

Blood Shadows: good damage to start with (the only 4[W] assassin power at this level) will grant you extra mobility for a while (unless enemies target the shadows, losing attacks, or can catch them in blasts/bursts).

Death's Doorstep: it's a weapon vs. reflex power and the damage is good, but the rider is valuable only against a monster that you expect to miss very often. Anyway as you'll mostly use this daily against an elite or solo you'll usually go up to 4 shrouds before invoking anyway so the real advantage is 1d6 every 4 rounds.

Shade Venom: you can get some serious extra damage out of this attack. Remember that if you compel the target to attack itself you cannot make attacks of opportunity against it. It will not work with undead, unless you can ovecome their immunity (via Venom Hand Master or later via the 22nd level utility Assassin's Eye).
Sundered Shadow: delivering melee powers from a distance is great. You get a +2 power bonus to attacks against the target until the end of the encounter and the base damage is good. Be careful as the main rider triggers only on a hit so try to make sure that this power lands. There is only one case in which this power is not extremely good: if you use a Blade of the Eldritch Knight (which is one of the best weapons for an assassin as long as the current wording stays). 

16th level utilities:
Assassin's Defense: +2 to the defenses will not make the difference often, but it may from time to time negate an hit. You get a short time invisibility. It's an encounter so that's a plus. You'll probably prefer this one to Liquid Shadow if you have the Assassin's Cloak feat as that can make this power blue.

Diehard (Endurance skill): a very good daily utility for non-revenants. You are not dying below 0 HP but you are dazed. 

Liquid Shadow: halving damage is always a good thing. You also get a teleport that can help you in repositiong if you're hit in melee or go after your target if you're hit at a distance (as the teleport has no range limit).

Gloaming Call: really good mobility power and it's an encounter. Ok it triggers only when you take damage, but make you teleport and become invisible!! And the range is fantastic (10). Useful to get to targets behing enemy lines. Put a gloaming near them, then the first time you get hit teleport near them and become invisible (and hide if you have Assassin's Cloak). 
Shadow Meld: your last ditch defense. It is good to have such a power in your pocket when things really get troublesome. You'll get yourself one round of peace and remember that even if enemies do not have line of sight and effect to you, you still have both lines to them.

Thief of Names: the combat effectiveness of this power is low as it only works with humanoids of medium or smaller size and you can share the damage only if you are adjacent to the target, but the out of combat potential, depending on your campaign, can really be huge. Clearly if you run a Dungeon Delve this power will not help you much, but in a more "traditional" campaign if you tweak out your bluff skill you can really become a con artist. Due to this reasons I will not rate the power here. In pure combat I would probably rate it purple, due to all the limitations.



17th level encounter powers:
Mob of Shadows: a strange isolating power with a rider for Bleak Disciples.  This power can even be Blue for Bleak Disciples, but only if your group has a consistant way of moving enemies into the zone, otherwise once again you'll have to rely upon your DM.

Shadow Fire: damage is ok (nothing special) but at this level you'll probably have some extra crit damage that starts to make a difference (a Vicious Fullblade?). You also get invisibility until the end of your next turn. Be aware that this power deals fire damage, probably the most resisted kind of damage around (and there's no feat like Venom Hand Master for fire damage). 


Shadow Knives/Shadow Knives: currently the CB/Compendium version of this power is different from that on Dragon 388 but no official errata has been made. This power is sky-blue in the original version and probably only purple in the CB/compendium one which is limited to one single attack. The comment here below is for the original version. The CB/Compendium version is utterly horrible.

a great encounter power. You get a bunch of melee attacks as targets start their turns, slow and daze on a hit. If you delay next round you may get other free attacks. Teamed with Spectral Assailants on an AP and Polearm Gamble may give you some more free attacks. The only limit is that i block line of sight for your buddies. Very good for Bleak Disciples: you'll probably be the best target for the enemies (slowed and dazed they'll probably decide to attack you if they are adjacent) but will get THP each hit, so you may soak up quite some damage.



Shadowed Deception: you can hit at a distance, the damage is very good for an implement power and the target grants CA to everybody until the end of your next turn (for Nightstalkers). It has the Psychic keyword so characters with Psychic Lock will inflict him a penalty to hit as well. For Bleak Disciples it's probably green.
Traitorous Shadow: damage is in line with other powers and the rider is nothing special. It is probably intended to deter artillery, but after falling down they can simply use a move action to get back on their feet. Or they can accept an OA and shoot at you anyway or resort to a melee attack if they have it. You have better alternatives at this level for both Guilds. 

19th level daily powers:
Consign to Shadow: this power seems to be conceived to create a sort of duel between you and the target. Well, forget it. Target a relatively weak monster, ask your allies not to kill him (they will tend anyway to concentrate on more meaningful targets) and enjoy insubstantiality against the meaningful enemies until the end of the encounter or until you can't sustain the power. Useless against solos.
Executioner's Blade: solid damage and reliable (the main point being the latter). Unless you can exploit it in some way anyway the damage is nothing special. If you can almost ensure you hit (for example because of bonuses you can get from a leader or from Soul Thief'Action) then Phantom Assault is much better. 
Guild of Shadows: in long encounters with many enemies it will outdamage any assassin daily of this level. You can use your conjurations to control the flow of the battle by positioning them.


Murderous Shadow: this summoning is insubstantial so it's quite sturdy. It has a quite good close burst attack and can get you free attacks if you place it properly.


Phantom Assault: absolutely great against solos, not so much in encounters with many enemies.

At 19th level you will more or less to decide between insubstantiality, solo-fighting or mass-fighting powers. Try to balance what you have here with the powers you already took in order to have a good card to play in every kind of fight.

Epic Tier Powers

22nd level utilities:
Claim the Dead: this seems a nice power and maybe it is. The main question is: how many times it will be you delivering the killing blow? As your DPR will not be very high it's an important point. All else in this power is great. I guess anyway it will trigger with a good regularity over the day, unless you're in a party of heavy hitting strikers.

Soul of Death: it's an interrupt and you get up to four shrouds on a creature you can see. It's the defensive daily version of Claim the Dead but you know it will trigger when needed. Most of the Revenant builds will not be interested in this power as they will be able to operate at negative HPs.

Assassin's Eye: great power. Many of your interesting powers (say Well of Shades) have a damage type and if you face immune or resistant creatures you may be unable to use them, but with this power for two rounds you will ignore resistances, immunities, penalties to attacks and so on. If you go for the Venom Hand Master+Spiderkissed weapon combo then this power will help you only with non-poison implement powers (waiting for a clarification from Wizards about weapon properties adding or not the keyword when used as implements). If you take this utility a power like Shadow Fire can become blue.
Fortress of Shadow: invisibility for one encounter if you can sustain it with a minor. Be careful with monsters that can stun you, because you'll lose this power as you'll not be able to sustain it. By the way at these levels the number of monsters with tremorsense/blindsight/truesight starts to grow and the effectiveness of invisibility starts to decrease.


23rd level encounter powers:
Cruel Shadows: the damage is the standard for this level, but the sliding rider is good and Nightstalkers will get CA for the whole party over the target for one round. 
Obsidian Spiders: the damage is potentially high if you can hit more than one creature. The fact that poison damage is resisted by many creatures should not bother you at this level. The rating is based on you having Venom Hand Master, otherwise it's probably green or even purple as you don't have anything on top of damage.
Shadow Swap: it may convince a stunning monster to leave you alone for one round, but timing this power may be tricky. For example it can avoid a dragon using its frightening aura not to be stunned in return, but in general I don't think it's very useful. High level monsters have a lot of choices about what to do.

Wraith's Assault: a good mobility power with the standard damage for this level.


25th level daily powers:
Assassin's scalpel: the crit range is interesting, but if you miss you inflict only a little shroud damage. And if you hit but you don't crit? Will you really lose the damage and try again next round hoping for a crit? 
Folded Shadow: great power as it will give you insubstantiality for a long time and can influence enemies so that they avoid attacking you.  The damage is good, too.

Reaper's Touch: can inflict serious damage to one target but unfortunately it's necrotic and many monsters will either resist or be immune to it, unless you go for Spiderkissed + Venom Hand Master.
Wall of Death: this is a party friendly wall and as it influences all the adjacent squares it can effectively have an area of 7x3 squares. Over the course of an encounter it can pile up a lot of damage and it can be exploited by all the forced movement powers your party probably has at this time. The only defect is that it inflicts necrotic damage which can be resisted by some kinds of creatures. Using a Spiderkissed weapon as an implement will bestow the poison keyword on this power making it sky blue with Venom Hand Master.

27th level encounter powers:
Ambush from Thin Air: damage is standard and do you really want to teleport yourself in a place you can't see without knowing what's there? The only possible interesting use I can see for this power is teleporting out of a creature who has swallowed you as you normally have no line of sight from inside it. Otherwise you only get a long range teleport to you assassin's shroud target.

Last word: depending on the the number of shrouds it can mean up to the equivalent of roughly 2[w] more. Perfect Slayer may exploit this power further via their 26th level utility.

Reaper in black: for nightstalkers. You can slide 3 a potentially big number of enemies. Very useful for control. Green for Bleak Disciples who get only a slide 1.

Shadows of doom: for Bleak Disciples this can be nasty against monsters with a big actions allotment (say solos, but also elites). For Nightstalkers it's probably green.


29th level daily powers:
Doom foretold: a solid damage power. You'll probably use it on an unshrouded enemy to go immediately to the maximum shroud level. Overall it will make more damage of Intent to Murder.
Intent to murder: I hate this power! It should be the assassin's killing blow but since you have no way of making your target helpless, you will deal a maximum of about 70-80 points of damage (a little more than half the DPR of an optimized ranger at this level). And RAW you can't add most of your static bonuses as there is no damage roll. It can be interesting against helpless targets but you'll totally depend on your party to get that condition.
Shadow Puppet: domination is always good and you can get some extra damage out of this power if there are creature adjacents to the target. 

Three Shadow Venoms: the target is dazed (save ends) even if you miss. If you hit it's weakened and takes ongoing poison damage 15. This is roughly equal at minimum to a 4-5[w] power plus three different effects and the target has to make three different saves. A lot of control and reasonable damage. The usual remark about poison powers: some creatures are immune and though the base damage of this power is untyped, the ongoing is poison so take that into account.

A small comparison between Doom Foretold and Intent to Murder. Let's take a Bleak Disciple with 28 Dex, 26 Con,a Fullblade and Thoughness. It will have 167 HP, with a bloodied value of 83.
Intent to Murder will then inflict 83 points of damage as we have no damage rolls.
Doom Foretold: 7[w] means 45,5 points + 9 (dex) + 6 iron armbands + 3 (weapon focus) + 6 (enhancement ) equal to 69,5 points. Then we have four extra shrouds that during the next round can be invoked for 33,25 points of damage (considering a 50% chance to hit) thus bringing the total to 102,75 HP. Any other bonus to damage rolls will increase the difference and for a Nightstalker it would be higher from the start, due to lower Con and HP and the Nightstalker bonus adding only to Doom Foretold. And Doom Foretold can crit too.

Feats

Assassin feats:

Heroic Tier

Assassin's cloak: considering the number of invisibility powers this feat will let you hide very often. Usually you can hide only at the end of a move action but with this feat you can do that on the spot when you become invisible. Check exactly with your DM the interpretation he has of the Stealth rules, as this can influence this power.

Assassin's escape: one of the best assassin's feat. Halving damage when you need it can save your life. Even better for Soul Thiefs who can recover Shade Form.

Avernian Emissary Wrath (Tiefling): for nightstalkers. Almost useless for a Bleak Disciple (but Tiefling Bleak Disciples won't be popular anyway). It's usefulness decreases as you go up in tiers, so you'll most likely retrain it sooner or later.

Betrayal of Zerthimon (Githzerai): ok, it's Combat Advantage for everybody on the creature for one round, but you have to act before it on the first round of combat and your buddies will need to be able to engage it.

Blood Devourer Shifting (Shifters): more or less the same considerations of Avernian Emissary Wrath, with the exception that this one is ok for both Guilds, being based on Dex.

Brutal Shroud: this one will increase your DPR by approximately 0,5. Is that worth? Maybe at low heroic but not later. A little better if you can increase your shrouding rate.

Close to Death (Revenant): pretty good. As a revenant you'll probably be able to be bloodied often and this feat removes one of the main limits of Shadow Step (you still need to end teleport adjacent to a creature though).

Concealing Shades (Revenant): the blue rating is for revenant assassins who have Thin the Herd and Reaping Renewal. Concealment in a wide area twice per encounter is absolutely good. Less effective if don't have the other two feats.

Crimson Eye Action (Human): interesting during the heroic tier (maybe blue there), but you'll most likely retrain it later. If you have taken the Slayer's Endurance 10th level utility and you're a Nightstalker you can upgrade this feat to green as it will help you in getting some more THP from time to time.
Dawn Hunter Training: it's difficult to evaluate this feat but if you roll really bad on a high [w] power (or 4 shrouds) it may be good to have a chance to reroll damage.

Darkness' Wings (Shadar-Kai): darkvision at heroic is good. Shadow Jaunt will give insubstantiality anyway and you get an unrestricted teleport. Good synergy with Hunter in the Gloom against high AC/low Ref monsters.

Darting Shade: you'll not often be in shade form as it ends as soon as you attack, so not very useful.
Death Sight: you can ignore cover and concealment when you attack a bloodied creature. Not that bad, but quite situational.

Death Walk (Revenant): you can get two extra teleports per encounter if you have Reaping Renewal, thus saving two move actions. Anyway normally you're not really lacking move actions anyway and don't have really too much use for them.

Death Wastes Nothing (Revenant): mmmm.... It's quite situational. You'll probably want this only if you have Grave Dust Assassin and can kill your target with a strike powered by Dark Reaping, thus transferring the shrouds to another target in order to invoke them later. May help also in some cases where you want to change target, but overall I would not recommend it.
Emerald Scale Concealment (Dragonborn): the main reason to play a Dragonborn Assassin. You can become invisible to many target once per encounter as a minor. Unfortunately lasts only until the end of your turn.

Eilserv's Treachery (Drow): Shade Form is a powerful feature especially for squishy Nightstalker as a drow will probably be.

Eternal Void Memories (Deva): the feat itself is not bad, being in line with racial assassin feats of Tieflieng an Shifters. Anyway Devas are not the best assassins around.

Far Shadow (Drow): adds range to Cloud of Darkness.

Flickering Fortune (Githzerai): Shade Form is a already a minor action. Very situational feat as you may not want to use it when you use your second wind.

Ghostly Voyage (Wilden): another source of insubstantiality. Good only if you have at least an encounter close/area power.
Grave Dust Advantage (Revenant): similar to Crimson Eye Action, so more or less the considerations are the same. Maybe blue at heroic, but losing steam afterwards. If you take Reaping Renewal at Epic it downgrades to green only, as you can use it twice an encounter (better than the other 1 shroud/encounter powers).
Grave Dust Assassin (Revenant): this feat stays solid over all your career. At heroic it's one of the main tools to get spike damage but also at epic you get potentially 4d6+24 points of damage.

Hidden Insight: it can be a little situational and to many people it may seem a feat tax. Anyway if you want to play the sneaky assassin it's a nice one. It can also help you in avoiding becoming a target of your assassin's shroud target if you don't want to engage him directly. Your DM may let you forego this feat and automatically add shrouds without the target noticing. Check with him as in that case thise feat becomes useless.

Horned Nightmare (Minotaur): you'll not charge often, but iy may have some use to by-pass obstacles outside combat.

Horns of the Shadow Reaper (Minotaur): honestly given your low strength you'll not use your racial often as you'll better use a different power.
Hungry Sky Shadows (Goliath): if you invoke every two rounds it will increase your dpr by 0,5 with a 50% chance to hit if you have a +2 Str bonus. As you'll probably not go much higher in Str the benefit is not so high and really disappears at high levels.

Hunter in the Gloom (Shadar-Kai): equivalent to a +2/+3 to hit for one round each encounter if you use a power that targets AC. Useful to increase the hitting chance of encounter or dailies.

Hunting Shadow (Wilden): teleporting is slightly better than shifting, but the damage kicker is low and you can't control it.
Initiate of Three Masks: as a changeling you're most likely increasing your Bluff anyway and you already get a racial bonus by the way. Maybe interesting for Changeling Bleak Disciples.

Insidious Shroud (Changeling): another one-shroud-per-encounter feat and it may be useless as it triggers only if you make the bluff check.

Leaping Shadow: you'll get some extra teleports from it. Anyway it can be wasted if there's no other creature adjacent.

Lolth's Embrace (Drow): a brother to insidious shroud. 
Keeper of the Black Flame (Drow): another "one extra shroud"per encounter power.
Killer's Insight: slightly better than Crimson Eye Action as you can use it every encounter and not only with an AP. The considerations are anyway similar (so maybe blue at heroic and the losing steam).

Maw of the Hungry Killer (Gnoll): some THP and possibly a free teleport every time you kill your assassin's shroud target. 
Merciless Nature (Wilden): CA once an encounter on a charge or MBA is not worth a feat, especially as an assassin has no special bonuses on charges.

Mind of Flawless Sight (Kalashtar): ignore the penalty for concealment or cover on your target. Situational.
Mist Walker Illusion (Gnome): it helps you in having more access to your racial power which is a good one for an assassin.

Nightmare Killer: it doesn't stack with weapon focus on weapon powers (and you'll most likely take that) so you can apply it only to some implement-based encounter powers mainly good for Nightstalkers. If you take them all then you may look into this feat but it's not really great.

Nightmare Step: the "Nightmare" feats are real nightmares?. You can apply this only to some selected encounter powers (and the terrible Terryfying Visage) and the only effect you get is a slide 1 if you miss.
Obsidian Cave Recovery: great feat. Recovering Shade Form when you spend second wind as a minor is extremely good.

Phantom Blade Evasion (Halfling): good to move out of trouble, but in the end it's only one teleport more each encounter.

Quick and Dead (Revenant): solid feat especiall if you have Thin the Herd. Triggering Dark Reaping early in the encounter will add 1 to your Shadow Step range for several rounds. May save you an item slot, if you look at increasing the teleport range.

Raven Queen's Disciple (Revenant): it really boils down to a small amount of THP each fight. A little better if you fight in an undead-heavy campaign. 

Raven Queen's Sanction (Revenant): eeekkkk... Terribly situational and with low effectiveness. Not losing a shroud on a miss if you attack an undead or shadow creature??
Reaping Ki (Revenant): it's a source of damage on a miss, but it's very situational. First you have to activate Dark Reaping, and then you have to miss within the end of your next turn with a ki focus attack. Useless for weapon users. Ki focus users may plan to use it with an encounter area/close power, where you roll several attacks and you may miss one of them. Anyway Revenant assassins are usually feat starved and may want to look elsewhere.
Resolve of the Iron Terminator (Warforged): good. You get resist 1-4 against your assassin shroud target. 

Scions of Zarak Initiate: ok, you use Furious Assault even on a miss, but do you really want to spend a feat for that?

Seeker of the Devouring Dark (Drow): as you cannot have multiple assassin shroud's targets it's not very useful. Anyway it's automatic damage and may kill a creature before it can act.
Shadow Veil Assassin: there are exactly 6 assassin powers that will let you use this feat. If you take many of them you may look into this feat but given the mobility you already have I don't see why you should.

Shadow Veil Disappearance: same situation of the power above. If you take all the powers and have a source of continuos concealment (without using invisibility otherwise this feat is useless) you may try this feat. At very high levels if you have a Shadow Band it may be interesting.

Shadowforged Killer (Warforged): is Shade Form better than Warforged Resolve? Difficult to say so expending a feat to be able to make the change may not be a good idea.

Spirited Shadows (Drow): the increased range of Shadow Step when you start in your Cloud of Darkness may be a good idea to keep the distance from very dangerous melee monsters, or a way to move from the front ranks to some enemy controller/leader back in the ranks.

Swallowed by Shadows (Revenant): becoming invisible when you use Dark Reaping is already ok, but if you have Reaping Renewal and Thin the Herd, this one becomes close to sky-blue.
Twilight Phantom Step (Eladrin): increasing you fey step distance if you end up adjacent to your shroud target may be useful from time to time but it's nothing great.

Velvet Blade Trick (Half-elf): before being nerfed it was a great feat due to Versatile Master. Now it's in line with all the other "one extra shroud per encounter" feats.

Vengeful Shade (divine): so far really useful only for divine characters MC'ed in assassin or those few full assassins with a divine attack power.
Venom Hand Assassin: as it works only on a hit it deals in average damage similar to an extra shroud. 
Venom Hand Killer: if you take this feat you'll most likely go the full poison way (Spiderkissed Weapon + Venom Hand Master and maybe Venom Soul). Otherwise the interest in this power is lower and you may rate it purple. 
Venom Hand Master: this feat is potentially one of the most powerful feats around. To fully exploit it you will have to use a Spiderkissed weapon and wisely choose your implement powers, but ignoring all resistance and immunities is simply awesome. If you don't use a Spiderkissed weapon then it's probably green or purple depending on your choice of powers.

Venom Handler: poison resistance that scales up with tier.

Word of Shadow (Kalashtar): this feat will be mainly triggered at high levels when Will attacks are more common and by that time the damage will be small.

Paragon Tier

Death Shroud (Revenant): don't touch it. Only useful in undead heavy campaign and if you have a way to recove Shade Form or use it as an interrupt.

Death's pall: this will give you some serious bonuses to your defenses, but it's an incentive to shroud a "weak" enemy and not to invoke.

Drawn Shadows: useful to stay hidden. There are better choices, though.

Minion of the Dark: the usefulness of this feat varies a lot. For scouting in dungeons it can be great and you can act without problems even out of the radius of your party lights. That's the reason I rate it blue. If you mainly adventure outdoor during the day then it's more limited. If you're a drow...
Nightmare Master: you may get the chance to daze several times each encounter. It has the limits of the "Nightmare" feats as the number of fear powers is not huge, but dazed is an interesting condition to inflict. Mainly for Nightstalker who will gravitate more towards fear powers.

Fade into Shadow: it's an immediate reaction so you'll not be able to use Assassin's Escape in the same round. Nothing special.
Grave Step: if you kill a creature you can shadow Step as a minor for a round and you don't need to start or end adjacent to a creature.
Killer in the Crowd: getting cover from enemies is not bad at all. And ignoring cover granted by your enemies is good too. Normally to get cover you should stay close to melee enemies so better suited for Bleak Disciples.

Shadow's Inexorable Grasp: you'll do your best to avoid triggering this feat. Even Revenant Undying builds will not really benefit from it.
Specter of Death (Revenant): ok, even if you're a revenant you may become uncounscious by failing a (or more) death saving throws. Anyway you'd better spend your feats to avoid that (say Fierce Vitality?)

Epic Tier

Soul in shadow: nice feat. It will grant you +2 to defenses very often against artillery/controllers.

Untouchable Shade: absolutely great. Just remember to invoke first and then put a shroud on the target to enjoy insubstantiality against one creature at a time for the rest of your career. Combines pretty well with Death's Pall as long as you can stay adjacent to your shroud target.

Vanish into Shadow (Revenant): given the fact that you can usually teleport each round this is almost equal to continuous concealment (it's not exactly equal, because it  lasts until the start of your next turn so you'll come out of hiding for example, and you'll need total concealment to hide again, but defense-wise it's the same as concealment as long as you can take a move action each round).
Walker Through Shadows: the question is: how often will you be insubstantial? If you use Shade Form for scouting (maybe with a Shadow Band and Darting Shadow at epic) then phasing can be really useful. If you are an Undying Revenant with Ghostly Vitality then you'll often be insubstantial.

Other feats:

Heroic Tier

Aberrant Mark of Contagion: you need to hit with a daily to trigger it. As you may have many powers who deal ongoing damage this can be an interesting feat.
Action Surge (Human): useful to place dailies. A well known and appreciated feat.

Armor proficiency Hide: green for now (not yet checked the enhancements available).
Bloodthirsty Mien: for Nightstalker's. If your DM uses the Intimidate rules for surrendering this may be an interesting feat given your high Cha.

Bolstering Breath (Dragonborn): this lets you use Dragon Breath without fear of hitting your friends. To look into this one you should already have Emerald Scale Concealment.
Dakshai's Body-Mind Union (Githzerai): this may prove invaluable over time. It may save you once an encounter from a nasty save-ends effect (stunned anyone).
Death's Blessing (Revenant): a situational feat. Anyway being able not to drown underwater is always a good thing.

Death's Quickening (Revenant): this feat is blue at heroic, when combined with the second level utility Fast Hands. Draw an healing potion as a free action, drink it as a minor and use your standard to go on beating the hell out of you target. Depending on your build evolution, this feat may become useless at paragon and will be for sure replaced by Ghostly Vitality at Epic
Diabolic Soul (Tiefling): you get a very nice daily power instead of your racial. Regeneration goes a long way towards being an effective assassin.

Durable: you need a little experience before looking at this feat. If you find out that you run out of healing surges before your allies you may look into it.

Enlarged Dragon Breath (Dragonborn): Dragonbreath is an interesting power, for Emerald Scale Concealment and damage with a minor. A bigger one may be useful.
Focused expertise: to some this is a feat tax, but almost nothing is better than +1/+2/+3 to hit. 

Githzerai Blade Master (Githzerai): proficiency with the bastard sword, the fullblade and +2/+3/+4 to damage!! The best weapon and the best to damage bonus for only one feat.
Human Resolve: for nightstalker's only. 3+Cha THP every time you spend an action point. Good at heroic, loses steam going up in levels.
Improved initiative: starting first is always important. You will usually have an high initiative bonus as Dex is your primary but this feat can make the difference.
Improved Razor Storm (Bladeling): a burst two power that inflicts good damage (Dex based) and ongoing as well as a minor. Works very well in a combo with Well of Shades and you don't need an action point.

Instictive Darkness (Drow): good to avoid bad situation (being surrounded). Activate it when the first enemy hits you and draw darkness upon you.

Ki Focus Expertise: you'll need to focus on implement powers if you take this one, otherwise Focused Expertise gives you a better option. The damage rider is nice as you'll get it 50% of the time. The bad thing is that your only implement at will (Executioner's Hood) is not really strong.

Life on the edge (Shadar-Kai): the Shadar-Kai version of Action Surge. +2 to hit and damage on an action point action. Solid.

Lost in the Crowd (Halfling): this will help you often if you're in melee. Usually Nightstalker will try not to be in melee so often (and Halfling will mainly be Nightstalkers) but the benefit is still there.
Knife in the Dark (Drow): you can get some nice damage out of this with blast/burst powers.
Mark of Shadow: good in many cases to stay hidden or invisible.

Mark of Passage: one more square of teleport for you. Interesting if you don't want to invest in a teleport enhancing item.

Melee Training: you'll often be in melee and very often invisible/hidden so you should get opportunity attacks regularly. This feat helps you in hitting and dealing damage.

Miryath's First Strike (Githzerai): better than the extra-shroud feats at heroic, and most likely still better at epic. At heroic it's at least blue.
Nimble Blade: this feat is mainly useful for assassins who multiclass into Rogue. You will have to use smaller weapons but +1 to hit is not bad considering that you'll be able to get CA very often.
Power Attack: this feat is usually a crappy one, but for one specific build, Githzerai/Storvakal PP it's sky blue as you will be able to ignore the penalty and enjoy a nice damage bonus, in particular if you use a two-handed weapon like most assassins will do.

Plague of Chance (Halfling): this will deal some damage every time you use your racial if you have Sudent of the Plague and has the chance to make you invisible if the reroll misses.

Plagueforged Accuracy (Elf): blue if you have student of the plague as you can get some good "area" damage.

Plague Regeneration (Longtooth Shifter): increases your regeneration rate and deals automatic necrotic damage to adjacent non-minions when you regenerate. The main drawback is that you have to be bloodied but avoid to go below 0HP, so its effectiveness will vary from encounter to encounter.

Plaguing Bloodhunt (Tiefling): simply great. It's extra necrotic damage against all bloodied enemies. If you have student of the plague it's extra fire and necrotic damage so enemies will to resist both to avoid it.
Reaper's resistance (Revenant): scaling necrotic resistance. Given the high number of monsters who deal necrotic damage can be good.

Restless Dead (Revenant): honestly you'd better take this feat at epic, where you will be often at negative HP.
Scrappy (small size): +1/+2/+3 bonus to damage that stacks with Weapon Focus (it's untyped). You'll probably have to take proficiency in the bastard sword but that's not a bad idea anyway. If you later multiclass (at epic probably)  into Fighter you can also look for Small Warrior's Defense.

Secret recovery (Drow): nice feat. More chances to hide even if you've used up all your actions.
Shadow of the Wild: this feat's effectiveness heavily depends on the campaign. If it's outdoors based then this is a no brainer. Hide, keep concealment (there are many ways to do that), optimize stealth and you're done. Not even your buddies will notice you.

Sturdy Shifter (Shifter): this can pull out a reasonable number of THP every day.

Thirst for Battle: a strange combination of Improved Initiative and Durable. May be an alternative to the first one.
Thoughness: you have controller HP. This feat will increase your HP pool by at least 10% in average. 
Vistani Heritage: this gives you a nice minor action that can keep a baddie away from you and gives you CA against it. As you normally don't use minor actions too much it's a reasonable feat.

Weapon Focus: most assassins would like to take it, but poisoners will look into Venom Hand Killer and Githzerai probably into Githzerai Blade Master.

Weapon Proficiency: the fullblade is one of your best choices. High damage, high-crit property. The Executioner's Axe is another choice.

Paragon Tier

Beasthide Shifting (Shifter): resist 2 is not that bad especially if you're bloodied (you need that to trigger your racial).
Cloud of Poison (Drow): a nice feat especially as it is party friendly, targeting only enemies.
Death Scorned (Revenant): this feat is nothing special for most builds. It becomes Sky Blue for the Undying builds with the Avenging Haunt PP and Raven Consort ED. In that case you'll never die because of failed death saving throws and you'll be fully conscious.
Dwarven Durability (Dwarf): great feat for Bleak Disciples. It's less impressive at epic, but still very good.
Dragonborn Zeal (Dragonborn): it's almost like having Soul of Death 10 levels before. Requires Dragonborn Frenzy which may be a problem as that feat is not really great.

Eyedark Strike (Drow): good to blind solos and elites.

Fierce Charge (Gnoll): your at-wills are not devastating, but better than an MBA.

Fierce Vitality (Revenant): always good, but becomes much better with a Life Charm at epic. With that item you'll be able to always stay conscious at negative HP and never die of failed death saving throws, but you'll not have the chance to roll a 20+ on a saving throw.
Great Fortitude/Iron Will/Lightning Reflexes: better defenses always help. One of the first two will help you raise your low NAD (depending on your Guild it will be either Will or Fort).
Inescapable Force: this can be a very nice feat, as you'll most likely have a force at-will (Executioner's Hood). 
Lasting Frost: frostcheese maybe will not be one of the main options for an assassin but can still be a possibility. You'll not be able to exploit it as much as multi-attackers but should at least look into into it.

Paragon Defenses: +1 untyped bonus to all NADs. To be retrained later for Robust Defenses.
Persistent Poison: only for poison builds.

Psychic Lock: Nightstalkers may look into this feat if they take many encounter powers with the Psychic keyword. Bleak Disciples will most likely stay away.

Shield Specialization: if you use a shield this feat is blue. Most likely you'll be using a shield if you multiclass into Rogue and use a light blade to be able to apply Sneak Attack and use Rogue powers.
Thin the Herd (Revenant): blue if you already have Grave Dust Assassin. It will let you trigger Dark Reaping very easily. Almost useless otherwise.

Uncanny Dodge: negates the +2 when enemies have combat advantage against you. Requires 15 Wis so it may not be interesting for all builds.

Unnatural Stamina (Revenant): can be good, depending on the campaign you play. If you go for an undead killing campaign this can be a fantastic feat.

Unyielding Stone (Goliath): a bunch of THP every encounter (1/2 level + Con Mod).
Venom Master (Drow): extremely nice feat for poison builds. Vulnerability 5 poison until the end of the encounter. The rating is based on a poison build, otherwise look elsewhere.

Versatile Master (Half-Elf): your Dilettante power becomes an at-will. More details in the multiclassing section.

Epic Tier

Ancient Stone (Goliath): one round more with damage resistance (10) when you use Stone's Endurance.
Blind Fight: a pretty good feat against invisible/concealed creatures. Don't let enemies play your game.
Deathless Warrior (Shadar-Kai): this may save you from being dropped. Probably only for Bleak Disciples as Nightstalkers will not benefit too much from it.

Epic Fortitude/Reflexes/Will: +4 untyped to a NAD. Great feats even if a bit lackluster...
Fluid Anatomy (Changeling): crits are one of your main enemies. Being able to save against them is a powerful ability.
Ghostly Vitality (Revenant): if you take this feat you'll most likely have a way to stay conscious at negative HP (Fierce Vitality or the Avenging Haunt PP). In that case being able to take all the normal action and being insubstantial is absolutely great.

Lolth Blessed (Drow): regaining cloud of darkness on an AP can be very useful.

Peerless reaction (Githzerai): instead of using Iron Mind you can use Second Wind as an immediate interrupt! Remember the bonus to defenses from Second Wind too, it may negate the hit.Poison's Partner: dedicated poison builds may look into this feat (-2 to saves against poison effects)

Quori desperation (Kalashtar): this feat will let you play the revenant once an encounter.
Reaping Renewal (Revenant): blue if you have Grave Dust Assassin, otherwise it's probably not that interesting.

Robust Defenses: +2 to all NADs. Once again a bit lackluster but very effective. If you have taken Paragon Defenses you can retrain that feat for this one as they don't stack.

Paragon Paths

Here I will look at the four assassin's paragon paths and at the other PP who look interesting, so most of the ratings will be on the high side.


Assassin Paragon Paths:
Gloaming Dancer: this is all about mobility and you get plenty of teleportation powers. Anyway it's maybe a little overkill. Sinister Shadows is quite good as it affects shadow step and any other teleportation power with the shadow keyword, and shadow blend is good to ensure constant combat advantage.


Obsidian Stalker: this PP is based on mobility. You get a good degree of insubstantiality when you move and you can move through enemy spaces. The daily is solid (especially against teleporting monsters) but the utility is not so usefule, especially as a daily. Better for Nightstalker who are a little more fragile.

Shadowblade: it wouldn't be a bad PP without two big limits. The first one is the shadowblade that cannot be enchanted so you'll have to rely upon you Ki focus, and the second one is the fact that to collect a Gloom Shard you have to kill the target with your Shadowblade. Compare it with the Soul Thief's equivalent ability (at 11th you have to kill it, at 16th it simply has to die within 3 squares of you).

Soul Thief: this one shines. It can be played in many different ways. Look at ShakaUVM's Mrs. Tough Guy build for a defensive way of playing, recovering Shade Form, but also think about the big bonus to attack and damage granted by Soul Thief's Action. Especially good if your DM likes big encounter with many enemies. Slightly better for Bleak Disciples as they will usually be closer to the fray where enemies die. 

Venomed Soul: getting better after March's errata. The most exploitable features could be Venomous Action for Bleak Disciples, but the PP itself only gives you a daily power who can inflict ongoing poison damage, so you'll need to look for powers who can do that on a more regular basis. This means usually going for a full poison build with a Spiderkissed weapon and Venom Hand Master.  A duergar (having Infernal Quills as a minor) can start looking at this PP with more interest. For it this PP can become sky-blue. If you multiclass/hybrid and take encounter powers that inflict ongoing damage (turned into poison by the Spiderkissed weapon), then this PP is Sky-Blue as well.


Racial Paragon Paths:
 


Abiding Reaper (Shadar-Kai): a good choice for both guilds. You get to ignore the resistances of the target on an AP (including insubstantial) and shut down his regen for a while. On top of that you have an alternative (albeit irregular) source of THP ans some good powers, that combine resilience (saving throws and spending a surge) with increased damage (inflict vulnerability).



Avenging Haunt (Revenant): some nice features and a very good daily power. The real thing here is Unkillable, the basis of the undying revenant character. Combined with feats like Death Scorned will make very difficult to kill you at paragon. At Epic the feat Ghostly Vitality and eventually the Raven Consort ED will close the loop and it will be almost impossible to kill you.
Shiere Knight (Eladrin): for nightstalkers. The 11th level features are nothing special, but the powers are nice (except the daily maybe) and the 16th level feature will mean +2 to all defenses for the rest of your career as you'll almost always teleport to get the +2 bonus. 


Mercurial Assassin (Dragonborn): a good package. An extra move action when using an AP, bonus to speed and Stealth, an immediate action attack power, the changeling disguise, and a daily that looks like Attacks on the Run on steroids (one target gets poison damage and the other is blinded).



Storvakal (Githzerai): Rebalanced Mind will let you Power Attack all day long without penalty (most likely with a 2-handed weapon). Restoring Action will help you save, Probability travel is an awesome encounter and the daily is great against monsters with resistance/immunities. What's not to like in this PP?





Rogue Paragon Paths:


Death Dealer: the main target here are Slaying Action (gruesome with Knockout + Ap Coup de Grace) and Unfair Advantage (mainly for Nightstalkers, but not bad for Bleak Disciple with Cha tertiary). The powers are a bit lackluster.



Ghost of Eventide: if you get the Vanish into Shadow feat at epic you'll squeeze out some DPR from Twilight Accuracy. The powers are pretty nice too (the encounter is quite damaging as you'll often with the Thievery/Perception opposed roll, the daily is good against a solo and the utility is good being an encounter).



Warlock Paragon Paths:
Evermeet Warlock: for Nightstalkers. The powers are maybe not fantastic but the features are awesome. Feywild Wake combined with the Assassin's cloak feat may let you dance in melee if you do things properly.

Epic Destinies

Here I will look only at the interesting stuff so most ratings will be on the high side.

Champion of Prophecy: better for Nightstalkers due to the Cha bonus being unrelated to the Dex ones but good for Bleak Disciples too. An interesting capstone. Revenant Bleak Disciples may look into abusing the bonuses of Unstoppable Prophecy by staying at negative HP and failing death saving throws (the bonus is cumulative). 

Deadly Trickster: you naturally qualify for this ED. Epic Trick is a fantastic utility, you have daily rerolls and get a chance everytime not to expend your dailies or encounters. The capstone can be fun too (it's one of the few possibilities in the game to influence the DM's rolls).

Demigod: this is one of the best EDs for almost all the classes and the assassin is no exception. Bonus to your two main abilities, heavy regeneration as a daily, a life saving 24th level feature and Divine Miracle.

Eternal Seeker: very useful to take powers from other classes (many of your powers are a bit lackluster especially at epic). Nightstalkers will have a wider choice as Cha is much more used than Con for attack powers.

Free Soul: this ED is all about saving throws. Be aware that the compendium entry is wrong as it lists all features at 21st level while as usual they are at 21st, 24th and 30th respectively.

Harper of Legend: an extra action point, the ability to spend more action points against monsters who use action points (solos and elites), a defensive utility and the life-saving power as a capstone.

Perfect Slayer: the assassin ED. It's absolutely good for your purposes. Bonus to Dex, an utility that puts 4 shrouds on your target and maximizes the next use, a chance to stay up below 0 HP and kill your shroud target plus the capstone that completely changes the behaviour of the shrouds as they never leave your target when invoked (unless you want to).

Prison of the Winds: only for Bleak Disciples, but absolutely amazing for them. Bonus to Dex, Con and speed! Storm Surge it's a life saving ability that also pushes the surrounding enemies and knocks them prone. Storm form will get crazy with Revenants that have Ghostly Vitality and Fury of Heur-Ket is a daily stance that will let you fly and push and knock prone all the targets you hit with a melee powers.

Punisher of the Gods: this will help you mainly against solos and you'll not be able to exploit it as much as other classes due to the fact that crit-fishing is not you business, but it is still a solid ED for an assassin. The capstone, if you get there, is fantastic, especially since you use big weapons.

Raven Consort: this is the ED of the Undying Revenants (Shadar-kai). You only get a bonus to Con, but if you came all the way to this ED damage and hitting are not your focus. The target is the 24th level features who gives you cumulative bonus to saving throws and defenses everytime you fail a saving throws, plus access to a surgeless healing source. If you take Raven Consort you'll most likely too Avenging Haunt as your PP and your target is being the last man standing (basically an insurance against TPK).

Raven Knight: mainly for Bleak Disciples, with bonuses to Dex, Con and speed. Dark Scythe is a very nice daily utility. Fey Charging Shiere Knights will become ridiculous with Shadow Rush (not only high defenses, but also insubstantiality...)

Reincarnate Champion: there's an amazing racial feat support for assassins (look at how many nice racial feats are in the feat list). This ED will help you in getting the best there.

The Dark Sun corner

Here some thoughts about Dark Sun. As it is a pretty much special setting I will keep the stuff separate.

Races

Mul: Ok, no bonus to Dex but you get a bonus to Con (a secondary for Bleak Disciples) and to either Wis (good for Covenant Agents) or Str (good for opportunity attacks and some feats). "Born of two races" is good as both Human and Dwarf have good feats for an assassin. An extra healing surge is a good bonus as you don't have many and Incredible Toughness is an extremely powerful racial power.

Thri-kreen: Bonus to Dex and to a possible tertiary ability (see mul above). Speed 7 is always good.
 Multiple arms is good for assassins switching from a melee weapon to a crossbow. The racial is good too, as assassins don't have minor action attacks. By the way combined with Well of Shades can let you make some good combos (more later under the Gladiator theme). Limited feats support though.

Themes

Athasian Minstrel: here the main focus is on poison. The Venom Hand Master feat makes poison quite interesting for any assassin and this theme combines very well with the Venomed Hand PP (in particular with Venomous Action) as the are several powers that inflict ongoing poison damage (Draining Poison, Envenomed Weapon and Insidious Poison). You can then look into multiclassing into barbarian for multiattack powers to deal serious damage (a bonus to attacks equal to your Con-mod is huge even if you use Str to attack).

Gladiator: absolutely great. Here the focus is mainly on Savage Sweep and Bloody Blades. Since you usually use big weapons close burst 1 attacks are pretty good. Both powers have good synergies with Well of Shades and Spectral Assailants. A Soul Thief with an action point can make pretty good combos with these powers. A thri-kreen can add another round of attacks with its racial power.

Feats

Lotulis Feats (Novice/Expert): you have to use a lotulis instead of a fullblade, but you get two solid multi attacks. A thri-kreen can use a ki focus and switch from a fullblade to the lotulis when needed.

Sturdy Plating (Thri-kreen): resist 2 all when bloodied is simply great for an assassin.

Multiclassing and Hybrids

Ardent:

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Multiclassing feat: you get a daily healing power as a minor action. Solid.

Hybrid: you get the same healing power as an encounter, but you lose a lot on the assassin's features side. As you'll probably go Dex/Cha you'll have to take Con or Wis as you tertiary depending on your build.

Interesting Powers (N=Nightstalker B=Bleak Disciple H=Hybrid)

1st level augmentable at-wills

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Ire Strike (N,H): if you have some heavy-hitting companion this may be worth in the augment 2 version, especially if the party can focus fire. 

1st level dailies:

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Battleborn Acuity (B): simply great for Bleak Disciples. Maybe you'll not hit (but you'll deal half damage) but a +1 bonus to hit and bonus to damage  equal to your constitution for all adjacent allies until the end of the encounter (you have little use for minor actions) it's simply great. You can stay behind the front line and provide the bonus, while shrouding and using implement powers, or join the fight. 

2nd level utilities:

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Wellspring of Vigor (B or H with Bleak Disciple Guild Training): if you are a pure assassin you can use this to help a friend, if you are an hybrid you can use it for yourself and get a source of THP even if you don't use assassin powers.

9th level dailies:

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Passage of Swords (N, H): this depends a little on your group build but if you have some good melee buddies it can be great (rangers with Heavy Blade Opportunity and Twin Strike, anyone?).

16th level utilities (Raven Consort):
Only a side note here. Both Bountiful Life and Fortunate Recovery can be very powerful in the hands of a Raven Consort who has access to surgeless healing and can get serious saving throw bonuses.

25th level dailies:

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Corona of Battle (all): it's a standard action, but gives good bonuses in a big burst and regeneration too. Keeping it up only uses a minor and you don't use minors very much anyway.

Summons to Doom (N,H): this is great in a combo with Well of Shades and it attacks will.

27 level augmentable at-wills:

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Dismissive Strike (H): it's listed in the Handbook of Broken for a good reason. Only hybrids will have the power points to pull off the trick using this power twice, but it's still a terrible one. Check with your master for the interpretation of hindering terrain. RAW the trick works. In your hands it's even more powerful than in others. Use Wall of Death with a Spiderkissed/Mordant weapon as an implement to turn the wall damage into poison, Venom Hand Master to bypass any resistance/immunity and the next round pull the double Dismissive Strike trick with an action point and teleport any creature to death (and you don't even need to hit). Cheese! Cheese!

Feats:
Nothing special here. The ardent feats are in general small increments of what you have. Only hybrids may be interested in them as most require a Mantle.

General notes: multiclassing in Ardent is especially good for very though assassin builds, focusing on staying power and can provide extra leader abilities to the party. You become a strange striker/controller/leader that can perform pretty well in large parties.

Artificer: Int is usually your dump stat so multiclassing into artificer is not really good. You may look into some utilities (Vorpal Edge is one), but honestly you'd better look somewhere else.
The same for the hybrid as Dex and Int do not align well with the secondary abilities of each class.



Avenger:

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Multiclassing feat: Disciple of Divine Wrath is the easiest to qualify for and the best one. Great to ensure that dailies or combos with an action point do hit your targets. You can go crit-fishing with encounter powers (Shadow Fire and Flurry of Talons). You can get more uses of Oath of Enmity via feats and powers.



Hybrid: you get Oath of Enmity, but that works only with Avenger or Avenger PP powers. You hit point base will be increased and youll'not be that squishy. Unfortunately you'll be stuck with cloth armor, unless you take a feat.


Paragon Paths:
Covenant Agent: a solid PP. Shadow of the Gods is a powerful de-buff to enemies' saving throws and you can pull it off regularly. You get to ignore radiant and necrotic resistance of your shroud target and inflict ongoing radiant and necrotic damage on an AP. On top of that the powers are good. 
Interesting Powers (N=Nightstalker B=Bleak Disciple H=Hybrid)

1st level at-wills:

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Radiant Vengeange (H): good to get THP. 

Feats:
Deific Instrument is not very well supported so far, but as more holy symbols will be released the chance of something good coming out increases.
Oathbound Stalker is good to increase you teleport range when you approach your OoE target. Anyway this really becomes useful only if you can use OoE several times each encounter.
Hand of Divine Guidance: maybe the only way to increase an assassin's critical range aside of a jagged weapon. Better if you can use OoE for several rounds each encounter

Equipment 

Alchemical:

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Bloodstinger Poison/Deathcap Spores/Clear Path Mist: strictly for the Venomed Soul PP Bleak Disciples. Open with one of these and if you hit follow with an AP for an important power and enjoy a huge to hit bonus.

Armor:

Most the armors rated will be either leather or hide, as hide armor expertise may be of interest for some builds. If an armor requires hide armor expertise to be used it will be noted in the name using (Hide).

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Addergrease armor/Snakefang Armor: interesting for poison builds (Venomed Souls mainly). Pretty useless for others.

Armor of Dark Deeds: a way to get concealment regularly.

Armor of Sudden Recovery: turning ongoing damage into regeneration until the end of the encounter can be good.

Battle Harness: power bonus to intiative and you can retrieve an item or a weapon as a free action (this can be quite useful especially at low levels for drawing healing potions for Revenants)

Bloodcut Armor: when things get critical and you are surrounded, this can save your life. Combined with insubstantiality will let you eat up quite a lot of damage.

Dawn Warrior Armor: resist 10 against acid, cold, fire and lightning plus a retaliation power based on Con, so better for Bleak Disciples.

Deathcut Armor: you will get resist 5 to two very common damages (necrotic and poison) and will get a nice retaliation strike against somebody who hits you in melee. Better for Nightstalkers.

Displacer Armor: for an entire encounter enemies making melee or ranged attacks against you will have to roll twice for attacks and take the lower value.

Inner Warmth Armor (Hide): you gain resistances to two very common damages (cold and necrotic) and can give it to one all adjacent allies once a day for an encounter. It's a bit expensive but solid. Fantastic if you run an undead fighting campaign.

Lifeblood Armor (Hide): it would be good especially for nightstalkers. A bunch of THP after each rest.

Life Vine Armor(Hide): a last line of defense, letting you spend an healing surge as an immediate interrupt when you get critted.

Mirrorsheen coat: it will let you re-target a ranged attack from you to an enemy within 5 squares. Not bad but you'll have to decide before knowing if it will hit you or not.

Shadowdance Armor: this will be very popular. You can use your implement ranged powers without fearing OA and have a nice daily to reduce lighting around you. If you strictly go for melee powers look elsewhere.

Shadowflow Armor: the bonus to stealth is untyped and stacks with other items. You can become invisible until the start of your next turn once per encounter as a minor.

Shadow Hound Armor (Hide): insubstantiality once a day when you become bloodied (last until the end of your next turn).

Sylvan Armor: interesting mainly for the Stealth bonus. If you want to go for Stealth it may free you another item slot. The Athletics bonus is good too for catching hold while falling and swimming.

Trollskin Armor (Hide): regeneration until the end of the encounter is nice, but the armor is quite expensive and if you take fire or acid damage the regen is suppressed.

Arms:

When it comes to arms your first choice will be whether to use a shield or not and if you are willing to use a magical shield or go for bracers. I will then divide this section in two (bracers and shields).

Bracers:

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Bracers of Escape: a daily chance of avoiding a melee attack by teleporting. Very nice to avoid crits or attacks with nasty aftereffects.

Bloodthirst bracers: reasonable for nightstalkers. You add ongoing damage once a day to one attacks. Blood Disciples should stay away.

Bloodsoaked bracers: these can give you a solid boost to damage for one encounter if you go for melee powers. Over one day they are less effective than Iron Armbands, but in one single encounter they're stronger.
Crest of Vigilance Eternal: a daily chance to avoid stun or dazed by making a saving throw as an immediate interrupt. This can be a shield or bracers so it will be in both sections.

Diamond Bracers: in some selected encounters they can be interesting but if your opponents have attacks that deal different kind of damages they'll not be very useful.

Iron Armbands of Power: it's sad that such a lackluster item is dominating this slot for strikers. You will have a lot of melee attacks so this will help you quite a lot. 
Phylactery of action: reroll a saving throws against dazed, immobilized, petrified, restrained or stunned once per encounter.

Rapidstrike bracers: +2 item bonus to initiative and oce an encounter you can use an at-will instead of a melee basic attack.

Serpentine Bracers: you can get quite some damage out of these bracers when you use some of your implement powers (blasts and bursts). You need to be hidden to get the bonus but at 18th level you should be able to do that often.

Trollhide bracers: daily regeneration until the end of the encounter.

Shields:

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Bloodshored shield: good damage resistance for one round. Probably better than Shield of Protection because you need only a minor action to activate this one.

Netherdark shield: it's a nice object to blind enemies, but it's usefulness may be limited as you can easily affect your buddies. If all party members have access to darkvision then it easily becomes blue, especially the bigger version(burst 3).
Shield of blocking: damage resistance until the end of encounter against melee attacks.
Shield of fellowship: a solid blue for Bleak Disciples. You can become a source of THP for other party members. If you can attack from behind defenders you can lend THP to them while attacking from behid the lines.
Shield of protection: solid resistance for one round and you can give that to an adjacent ally too. Can save you from huge amounts of damage if you are surrounded. Unfortunately it's a standard action.

Shield of Ultimate Protection: +1 shield bonus to two defenses (Fort and Will) and for one encounter/day +5 untyped bonus to all defenses. Awesome! For some builds it will be worth to look for Heavy Shield Proficiency to get a +1 shield bonus to all defenses.

Divine Boons:

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Sehanine's Mark of the Dark Moon: the lowest level boon (8th level) already gives you the benefit, halving damage you get from attacks done by enemies who cannot see you. As you'll spend quite so time invisible this boon is very good. The cost is minimal and it doesn't use any slot.
Worshiping Sehanine is not a bad idea.

Dragonshards:

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Siberys Shard of Merciless Cold/Siberys Shard of Radiance/Siberys Shard of the Mage: the first two are sky-blue only if you use a Frost/Radiant weapon, while the Shard of the Mage is Sky-blue if you use many implement powers. They give you a nice boost to damage and do not use any slot.

Feet:

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Boots of Quickness: untyped bonus (+1/+2/+3) to your reflex defense. 

Boots of Stealth: a solid bonus to stealth checks (+2/+4/+6)

Dragonborn Greaves: +1 to AC and Ref and +2 to speed while you're bloodied. Revenants will get more use out of these, especially at higher levels.

Eladrin Boots: with these your Shadow Step becomes a teleport 5.
Lightstep slippers: close to epic boots of stealth. The bonus is 1 point lower, but the item is cheaper and you cannot be detected by tremorsense.

Sandals of Precise Stepping: the same stealth bonus of Boots of Stealth at heroic, falling back at higher tiers (+2/+3/+4). This bonus extends to Acrobatics and Athletics but the cost is higher.

Spark Slippers: blue for Nightstalkers. You can inflict lightning damage equal to your Cha modifier to any creature that moves adjacent to you. Over the course of a day this can amount to a sizeable figure.

Hands:

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Gauntlets of Blood: untyped bonus to damage against bloodied enemies. It applies to all your rolls, not only melee, and stacks with Iron Armbands of Power and Siberys Shards.

Gauntlets of Destruction: an alternative to Gauntlets of Blood at paragon. The overall damage should be close to that of the paragon version of the Gauntlets of Blood, slightly better if you use dailies with many [w] but you cannot apply the bonus to multi-target implement powers which are among the best things an assassin has.

Gloves of Ice: a solid boost for Frostcheese users. The rating is based on using a Frost weapon, otherwise these gloves are not that appealing. Still interesting though if you have powers like Well of Shades and Cloaking Mist, who can affect several targets but probably only green then.

Hero's Gauntlets/Great Hero's Gauntlets: these items can be an interesting source of THP and help you in hitting with APs. The Great version is maybe a little expensive for an item that wprks only on APs and provide THP only if you hit.

Shadowdancer Gloves: similar to Serpentine Bracers. An interesting item if you plan to be hidden often.

Head:

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Cannith Goggles: better than Headband of Perception at heroic and extremely cheap. At paragon/epic you'll probably move to the Headband if Perception is your focus with this slot.

Circlet of Arkhosia: rolling at the start of your turn as well as at the end against the worst conditions in the game can be crucial. Assassin's are fragile things and one round of inactivity can spell disaster for you.

Circlet of Indomitability: +1/+2/+3 item bonus to Will. Better defenses are alway good, but probably Bleak Disciples will be more interested in this one.
Coif of Mindiron: you can avoid being dazed (at heroic), dazed or stunned (paragon), dazed, stunned or dominated (epic) once per encounter. Less useful than the Circlet of Arkhosia if the monsters can use the power several times per encounter or at will, but better against encounter effects.
Eye of awareness: +2 untyped to Will and +5 item bonus to initiative.

Headband of Perception: +1/+3/+5 bonus to perception. Perception is usually important to you so this item helps.

Hood of the Wolf: +4 to perception, insight and intimidate and darkvision are all good for you. The encounter power is not bad too, especially against monsters with invisibility.

Fey-blessed circlet: blue for nightstalkers in late heroic/paragon. Some THP at the start of every encounter. At epic it won't make a real difference so you'll probably abandon it.
Goggles of Night: darkvision is always a good thing, especially if you like skulking in darkness. Useless for some races.

Ioun Stone of True Sight: +6 to perception and darkvision plus a daily sustainable power to see invisible creatures. It's quite expensive tough.
Lenses of the Luminary: a close friend to Hood of the Wolf. Bonus to perception, darkvision and some interesting charge-based powers.
Stag Helm: the bonus to perception is better than that of the Headband by 1, but this applies only to passive perception and not to active. You can take a minor action if you are surprised (activating a defensive item?). Overall very close to the Headband.

Shadowdancer's Mask: if you don't like the roll on a crucial stealth or bluff check you can reroll it with a +3 bonus.

Trickster's Mask: roll twice for Stealth and Thievery and once a day take 20.

Ki foci:

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Cup of Death Ki Focus: good addition of THPs for Bleak Disciples, plus a good encounter power.

Final Sleep Ki Focus: almost equivalent to a vicious weapon.

Iron Body Ki Focus: damage resistance until the end of your next turn against the attacks of the creatures you hit. Goes to Sky-Blue if you focus on blast/burst/area encounter powers (Well of Shades, Cloaking Mist, Obsidian Spiders) as you get resistance to the attacks of all the creatures you hit. The crit damage is solid too at 1d10 x plus.

Rain of Hammers Ki Focus: the extra attack can help on some situations but it usually of limited scope.

Scavenger Bird Ki Focus: a cheap version of this focus may be interesting

Legendary boons:

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Book of Truths (Fourth Truth): equal to the eye of awareness but it doesn't use you head slot.

Book of Thruths (Fifth Truth):  equal to Ioun's Stone of True Sight but it doesn't use your head slot

Silver Hands of Power (19th level): recover a daily or encounter power once a day if you score a critical hit. Interesting for Rogue multiclass build who take Knockout to exploit an high [w] power.

Neck:

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Amulet of Aranea: resistance to poison and a daily power that will benefit mainly Venomed Souls.

Amulet of Life: this item is strictly better than the Cloak of the Walking Wounded (unless you can use second wind more than once per encounter). It allows you to spend two healing surges instead of only one once per encounter.

Assassin's Cloak: rolling twice means in average a bonus of 3,325 to your stealth check. And an interesting daily invisibility power.

Brooch of Vitality: more hit points and an higher surge value as a consequence. Solid item.

Cloak of Invisibility: a powerful daily invisibility power, but nothing else. If you can pump your defenses some more (say with a Shield of Ultimate Protection) then you can make your character almost unhittable for one encounter a day.

Cloak of Resistance: resistance until the end of your next turn once a day. Good if you get surrounded and want to avoid a beating.

Cloak of Survival: resistance to cold and fire and a bonus to endurance checks.

Cloak of Translocation: this is almost a +2 to AC and Reflex for the rest of your career. Stacks with the Shiere Knight's Cloaked in Magic feature.

Death Defying Cloak: a life saving item, but not the best one. If you happen to be in the aura of some creature you'll be dying again at the start of your turn and any area attack will do the same.

Elven Cloak: an item bonus to stealth. Nice at low levels. At higher levels the piwawfi is strictly better. Personally I would use a different slot for an item bonus to stealth, but it can depend on your exact build.

Far-step Amulet: looks good, but it's more expensive that Boots of Teleportation and Shadow Step carries some limitation while the Boots let you teleport freely. Look at this item only if you really want more teleporting distance and want to use your feet slot for something else.

Life Charm: a good choice for all characters. Some revenant builds using the Fierce Vitality feat can use it to stay conscious at negative HP. Some others, who focus on automatic healing when below 0 HP by making a 20 or more on Death Saving Throws will not want this item.

Mantle of Faith: a life saving item, but it's an immediate reaction, so will not heal you if the attack brings you below 0 HP.

Medallion of Death Deferred: another life saving item, but this one is a no action and actually heals you some more HP.

Periapt of Cascading Health: you can end a condition on you once per encounter. Unfortunately doing that it's a minor action so this item will not help you against the worst conditions (stunned and dominated).

Periapt of Proof Against Poison: well, as the name suggests, you get poison resistance.

Periapt of Recovery: +2 to Death Saving Throws. All characters will benefit from this item as it triples your base chance to automatically recover from the dying condition when you make a saving throws. Good also for some revenant automatic-healing builds.

Piwafwi: bonus to stealth and fire resistance.

Possum Amulet: similar to the death defying cloak and with the same drawbacks.

Raven Cloak: resistance to cold and necrotic + a daily reroll on a save with a +5 or +10 bonus (if it's a death saving throw). Very good item and Sky-Blue for undead heavy campaigns.

Scarab of Invulnerability: it's quite expensive and has only a daily power, but it's invulnerability until the end of your next turn.

Steadfast Amulet: a daily chance to roll a saving throw as an immediate interrupt to avoid being stunned or dazed.

Tattered Cloak: a nice daily power to become invisible to many targets. But you have to hit.

Tenebrous Shroud: necrotic resistance and a daily invisibility power.

Rings:

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Chameleon Ring: the base property is nothing special but the daily power is solid. 
Eladrin Ring of Passage: Shadow Step becomes a teleport 4 or 5 (if you're an Eladrin) and the cost is relatively low. You also get a teleport that doesn't require line of sight, which is very useful in those bad situation when you get swallowed by a monsters.

Ring of Dimensional Escape: also this one makes Shadow Step become a teleport 4 and you get a free teleport when you go below 0 HP which is especially good for non revenants (who at this level will most likely be able to stay in battle even below 0 HP). More expensive than the Ring of Eladrin Passage, but can potentially save your life and is still in the paragon tier.

Ring of Free Time: resist 5 to all is the main issue here. The extra minor action is good too, but a pure assassin has not much use for minor actions. Multiclassing may change this.
Ring of Giants: better that War Ring in many cases, but you should look into this one only if you have a way to do some crit-fishing.
Ring of Invigoration: a life saving power. I have some doubts about the wording though. It's a free action, but you can take it only when you are reduced to 0 HP and if you're dying you should be able to take free actions. RAW it's interesting only for revenants, but I guess that RAI everybody should be able to use the power when brought to 0 HP.

Ring of Protection: +1 item bonus to all saving throws. The daily is nothing special.
Ring of Regeneration: +3 to your healing surge value, and a daily recovery of one healing surge and regeneration if you've reached a milestone.
Ring of Retreat: this is probably the only item who can save a party from TPK (ok, this works only from the 5th encounter of the day, but very often TPK happen there, when the party is low on surges and has used up dailies). You get also a 1 square increase to all your teleports. You can also use it to access items you stash home (hey, we're out of healing potions...let's go home and take them). 
Ring of Tenacious Will: sky blue for Nightstalkers. You can use Cha instead of Con to determine your healing surge and get a life saving power that heals a decent amount of HP if you've reached a milestone. Less interesting for Bleak Disciples.

Ring of the Dragonborn Emperor: this ring can be used in a combo if you have a Battlecrazed weapon (even a low level one) and the Well of Shades power. With an AP you can do:
Minor: battlecrazed
Immediate Reaction: Well of Shades
Standard: Well of Shades and teleport out
AP: Cloaking mist
Minor (instead of Move): Dragonbreath (cold?) if you're a Dragonborn.
With Lasting Frost and the bonus to close attacks you get from this Ring you can inflict quite some damage to a group of monsters.
Ring of the Phoenix: resistance to fire plus a life saving power that heals you well, let you teleport and make a close burst attack based on Con or Cha (so good for both guilds).

Shadow Band: concealment all day long plus total concealment for one encounter. There are only two creatures that ignore concealment and they are both level 14 so you'll probably not meet them by the time you have this ring.
Shadowfell Signet: mainly for undead heavy campaigns.

Waist:

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Belt of Blood: blue for Bleak Disciples. Your healing surge value is increased by your Con modifier when you're bloodied.

Belt of Sonnlinor Righteousness: crazy for revenant builds. It really kicks in only in paragon when you put your hands on Fierce Vitality, but becomes broken if you can keep fighting regularly below 0 HP. Raven Consorts may be almost unkillable with this belt.
Belt of Vim: +1/+2/+3 item bonus to Fort.

Cord of Foresight: may be interesting for Nightstalkers, who do not generate THP. It lets you start every encounter with an healing surge of THP which is not that bad.

Potion Bandolier: potion juggling can help you especially at low levels. Revenants with Death's Quickening will make the most out of this item.

Sash of Regeneration: regeneration 5 while bloodied. 
Survivor's Belt: rolling twice saving throws is better the more bonuses you have. This points towards unkillable builds. Raven Consorts rolling twice will become your DM's nightmare.

Weapons:

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This part is probably the most difficult of the whole Items sections. Any feedback about the ratings will be greatly appreciated. In some cases a weapon is listed not because you want it to attack, but because of a power you can use even with a low level version of the weapon.

Armbow: for warforged. No more bolts, free loading and the crossbow is a one handed weapon.
Battlecrazed Weapon: this will probably not be your main weapon, but you can use a low level one to trigger a some racial feats/powers, like Dark Reaping (with Thin the Herd to trigger Grave Dust Asssassin), the Shifter racials, or the Dragon Warrior feat). 

Blade of the Eldritch Knight: as all of your weapon attacks are standard action this blade really shines, letting you deliver melee attacks from 5 squares away. By the way it's part of the Eldritch Panoply and that's another reason for it to be an interesting item.

Blood Fury Weapon: as the battlecrazed but the power is an encounter. A low level one will be very interesting for those who have something to trigger by becoming bloodied. As you need it only for the power you'll most likely use a different weapon to attack.

Bloodthirsty Weapon: +1 to hit and extra damage equal to the enhancement bonus to bloodied enemies.

Frost Weapon: to exploit frostcheese by taking Lasting Frost.

Frost Fury Weapon: revenant Bleak Disciples may be interesting in this weapon as they will be bloodied often without too much risk and have high Con. By the way with the last interpretation of the rules when you are bloodied your attacks will get the Cold keyword so you may look into frostcheese. Probably too dangerous for a non Revenant.
Graefling: gives you darkvision and is brutal 1 against bloodied enemies. The main interest here is darkvision.

Graceful Weapon: look into this one only if you go crit-fishing with Daggermaster (a strange path but somebody may do that). Using you Dex mod instead of a dice is better.

Incisive Dagger: good to increase your Shadow Step range. Anyway remember that to get use of the property you'll have to wield the dagger and this will leave you only a one-handed weapon to attack. 

Jagged Weapon:  19-20 crit range. Deals ongoing damage on a crit.
Mithrendain Steel Weapon: another way to increase your teleport distance. Anyway you'll probably want to do that using some other item.

Mordant Weapon: great to bypass resistances. Obvious synergy with Venom Hand Master, but if you take the feat then you'll probably go for the cheaper Spiderkissed weapon.

Pact Weapons (Sword/Blade): if you want to multiclass into Warlock these will save you the cost of an extra implement. The sword is a longsword and for eladrins only and the blade is only a light one.

Radiant Weapon/Sunblade: going Morninglord to exploit radiant vulnerability by using one of these items is a way to get more DPR. For Nightstalkers, as the Morninglord attacks can be based on Cha but not Con or Dex.

Ravenclaw Warblade: when you drop a non-minion enemy you can spend an healing surge or make a save. Can be useful if your party is low on the leaders's side.

Rubicant Blade: +1 to Shadow Step and an interesting daily power to teleport up to two allies. This can be useful to teleport an unconscious ally close to your leader(s).

Shadowrift Blade: will not rate this one yet. Some interest about "slashing" assassin builds seems to be around. Still to see something solid but it's better to keep this possibility in mind.
Spiderkissed Weapon: the basic weapon of the poison builds and sky-blue for them. Take it only if you have Venom Hand Master to bypass any resistance or immunity.

Subtle Weapon:  you'll attack very often with combat advantage and this can help increasing your DPR. Stacks with everything.

Sword of Black Ice: only an high level version exists, but it's a very good one. It's a longsword but it deals 2d8 poison damage extra on each hit as a property, thus bestowing the poison keyword and triggering Weapon Hand Master. The crit damage is good, dazes on a crit and once a day you can stun (save ends) the target when you crit. By the way the wording of the dazed effect is unclear as no way to end the condition is listed. Extremely good if you want to use a shield.

Vicious: can be your choice at low levels when interesting enhancements are not really available.
Wraithblade: this is useful only for MC Rogues with Daggermaster and using a dagger. Blue or maybe Sky-blue for them.

Wyrmtooth Dagger: once again for Daggermaster. You can act as support for your buddies by trying to shut down enemy resistances.

Wondrous:

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Battle Standard of Healing: cheesy? Maybe. This item is cheap and useful at any tier. Unkillable revenant builds can keep a whole party up with this standard.

Darkskull: if your party has access to darkvision, then this item is deadly and may easily be a way to decide the build of a party. 10 squares in every direction is a lot of space. You'll be able to hide very often. If darkvision is not available look elsewhere.

Demonskin Tattoo: you get resistance to a type of damage you choose between acid, cold, fire, lightning or thunder until the end of the encounter everytime you use an action point. Solid especially because you can decide the resistance on a case-by-case basis and the tattoo doesn't use up any "normal" slot. 

Dice of Auspicious Fortune: depending on you luck on the dice this item can help you or not. Anyway I guess that a lot of epic tier characters will buy these dice.

Eager Hero's Tattoo: for Nightstalkers, to start each encounter with some THP.

Fireheart Tattoo: a cheaper and less effective alternative to the Eager Hero's Tattoo.

Mummified Hand: the benefit of another ring is good, but the cost of the Hand is very high.

Resurgence Tattoo: you regain the use of an encounter power when a non-minion crits you. Very nice property, but the cost is high.

Tattoo of the Escape Artist: the cost is low and if you get critted you can now teleport as a minor until the end of the encounter. If this happen you can start teleporting in and out of the fray.

Sets:

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Only some comments here about Sets that can be interesting. As you'll usually need to take more items to get access to the extra benefits, there are many combinations possible and each one could be taken or not based on your overall build

Shadowdancer's Garb: the single items are more or less usefule for an assassin, and the cumulative bonus to Athletics, Stealth and Thievery is pretty good. It's an item bonus though, so it will not stack with other item bonuses. Overall is a very nice set for the late heroic tier.

Zy Tormtor's Trinket Benefits: assassin/warlocks maybe interested in this set at low levels. Pact Blade helps in keeping costs down. Probably the Blade and the Prison or the Mantle will be your target to get the Thievery bonuses.

Eldritch Panoply: the Blade of the Eldritch Knight is great and the benefit you get with two items is equal to an extra teleport every round. The Rebuking Bracers are good too, as you will automatically teleport 3 your target and daze hit when you score a critical.

Offering of Celestian: to be evaluated for Hybrid Sorcerer/Assassins. 

Build

Currently the number of available builds is low. Some trends start to emerge, tough and I'll try to showcase them.

Unkillable Builds
These builds exploit the inherent toughness of the Bleak Disciples, based on THP generation, insubstantiality and invisibility, and that of the Revenant race.

ShakaUVM's Mrs. Tough Guy (beware the picture - remember I warned you): this is a paragon build that can eat up a lot of damage and win the battle by outlasting its enemies.


Coup de Grace buildsThese builds look at the Coup de Grace mechanic to slay targets outright.

Psk20's Black Ice Slayer: here the rogue power Knockout is used to make the target helpless and CDG is made with Every Trick in the book. Aside from that, this is also a solid Nightstalker build, where the main defense is being hidden as much as possible.

My Headsman: a Bleak Disciple Coup de Grace Build. It has good melee resistance and solid damage for an assassin, including a daily nova that can kill high level solos, using Hurricane of Blades (with an AP and Soul Thief's Action).


Hybrid Builds
Something is moving in this area after the rules came out.

Nox_Noctis' Assassin|Rogue/Warlock/Evermeet Warlock: with this build you'll be able to hide better than Nessie.

Covenant Agent builds:

Psk20's Covenant Agent: this build is using the Covenant Agent PP to go for crit-fishing with OoE, Two Weapon Opening and the nice multi-rolls encounter powers of the assassin.

Other builds

Chanter Hound's Cheshire Cat: an 11th level build with the Chameleon PP.

Squad's Charging Assassin: here a good DPR is reached by charging optimization and overall mobility to ensure you can charge as often as possible (encounter powers go for control mainly).