Fetchlings are a race descended from humans who had been trapped on the shadow plane, and therefore they have some unique darkness- and shadow-focused abilities. At first, fetchlings seem very similar to wayangs in this way, but the abilities of both races are actually quite distinct.
Ability Scores: +2 Dexterity, +2 Charisma, -2 Wisdom. These bonuses and penalties make fetchlings excellent as Ninjas and spontaneous casters, but they aren’t really made for prepared divine casters.
Type: Fetchlings are outsiders with the native subtype, which means that, just like aasimar and tieflings, they can’t be affected by spells specifically affecting humanoids, like enlarge person. This can be a huge detriment to buffing, but they also aren’t affected by things like charm person, so it can also be a boon.
Size: Fetchlings are the same size as humans.
Speed: Fetchlings move the same speed as humans.
Shadow Blending: This is a peculiar ability that will definitely come in handy for any character. In dim light, instead of the normal 20% miss chance, your enemies will have a 50% chance of missing you. This does not, however, equate to full concealment, so you still can’t do things like deal sneak attack damage just because you’re in dim light. Overall, though, this is a great ability, especially for a sneaky Rogue or Ninja.
Shadowy Resistance: Resistance 5 to both cold and electricity is a very nice bonus, so this is pretty sweet.
Skilled: You have a +2 racial bonus on Knowledge (planes) and Stealth, so obviously for a Ninja this is great. However, the Knowledge (planes) bonus can be replaced by a +1 to both Knowledge (nature) and Knowledge (local) if you choose the World Walker alternate trait, so I personally think that’s more useful, especially in PFS play, so I’ll leave this one green.
Spell-Like Abilities: Disguise self once per day is pretty cool, but the really awesome parts of this ability come at later levels. Starting at 9th level, you also get shadow walk once per day, and at 13th level you get plane shift once per day! Those are some seriously high-level spell-like abilities, and are a great option for any character. Pay attention, though, to the Gloom Shimmer alternate racial trait, which trades shadow walk at 9th level for displacement, which will be more useful for melee fighters of any type, in my opinion.
Darkvision: Darkvision is excellent, and you get low-light vision on top of it! Sweet!
Low-light Vision: In the case of the fetchling, you have both darkvision AND low-light vision, so they’re going to come in handy in different situations.
Alternate Racial Traits:
Emissary [Shadow Blending]: I suppose for a party face-type character this would be very useful, but honestly it just doesn’t compare to getting additional concealment in dim light. Keep Shadow Blending unless your only purpose in the party is to convince enemies NOT to attack you in the first place.
Gloom Shimmer [Alters Spell-Like Abilities]: This is an excellent option for any character who will be getting attacked fairly often, since it allows you to cast displacement once per day starting at 9th level. Now, if you’re in dim light, you’ve already got a 50% miss chance, but this is for when you’re in bright light that you just can’t get away from, or when you REALLY need to deal sneak damage on every attack for a few rounds. I like this option for front-line melee and Rogue-style characters more than others.
Shadow Magic [Skilled]: For spellcasters, this is a really good option, since you’re probably not going to be using Stealth in combat that often anyway, and there aren’t a ton of ways to boost your actual caster level for any given character. Obviously non-spellcasters gain nothing from this ability, and it’s red for them.
Subtle Manipulator [Alters Spell-Like Abilities]: If I was going to play a party face character, I would have a lot of trouble deciding between this and the standard spell-like abilities, because while alter self can let you infiltrate an entire room full of opponents, memory lapse can save you after rolling a natural 1 on a crucial Diplomacy or Bluff check. I suppose alter self is probably the better option overall. Notice that you can take both Gloom Shimmer and Subtle Manipulator if you want to, as they alter different spell-like abilities.
World Walker [Alters Skilled]: I think this is probably a slightly better option than the regular Skilled trait, since you’re getting bonuses to two Knowledge checks instead of one (diversity can be very good) and you still keep your Stealth bonus. The standard Skilled trait is still great, though, so there’s no clear “YOU MUST TAKE THIS ONE” here.
Alchemist: A fetchling can make for a decent bomb-focused Alchemist thanks to the Dexterity bonus, but without an Int bonus they’re never going to be perfect. You could also make good use of the Vivisectionist archetype with a fetchling, thanks to their sneaky nature, but if you were going to do that, I’d go Ninja instead in the first place.
Barbarian: With no boosts to either Strength or Constitution, and given a Barbarian’s generally non-stealthy approach to combat, fetchlings weren’t really meant to make good Barbarians. The exception to this would be the Urban Barbarian, who can use Controlled Rage to gain bonuses while still being able to use Stealth. Even in that case, though, a fetchling will never be an optimal Barbarian, so I’d look elsewhere.
Bard: This is a good class choice for a fetchling, thanks to the Dex and Charisma bonuses. I like the Magician archetype for a fetchling Bard thanks to the more arcane focus, and you’ll obviously want to toss out a lot of illusion (shadow) spells to make use of the boosted caster level.
Cavalier [Samurai]: Neither Cavalier nor Samurai make sense for a fetchling, as riding a mount is counterintuitive to their stealthy nature. You might do alright with the mount-less Sword Saint archetype, as it makes use of an enemy’s unawareness of your intentions to deal some extra damage in the first round of combat, but overall this is just not a great choice.
Cleric: A penalty to Wisdom means you’ll never be an optimal Cleric. If you do choose to make a fetchling Cleric anyway, the Darkness (Night) subdomain is an obvious choice, as it synergizes with your Shadow Blending ability, making you invisible to creatures without darkvision when you’re in an area of dim light or darkness. My suggestion, however, is to go Oracle instead.
Druid: Just like the Cleric, a Druid relies too much on Wisdom for spellcasting, and that Wisdom penalty really hurts. If you go down this road, the Darkness (Night) subdomain is an obvious choice, or you could take an animal companion like the giant chameleon who will get its own bonuses to Stealth while you hide in the shadows, tossing out spells.
Fighter: A ranged Fighter build will work just fine for a fetchling, especially with the miss chance in dim light. I’d highly suggest tossing a few ranks into Use Magic Device and getting a wand of darkness to make use of that miss chance as often as possible. You may also find the Dark Sight feat to be a good investment, allowing you to stand fifteen feet within magical darkness and still see outside that darkness clearly. You’ll have to take Gloom Sight first, though, which includes light sensitivity, so that is less exciting.
Gunslinger: Everything I just said for a ranged Fighter build applies to a Gunslinger, so this is also a great option.
Inquisitor: While a penalty to Wisdom doesn’t hurt an Inquisitor as much as it does a Cleric or Druid, you’re still not going to be optimal here. Obviously the Infiltrator archetype is both thematic and powerful in combination with the fetchling’s spell-like abilities. Overall, this is a mediocre option at best.
Magus: A Dex-based Magus build is a great option for a fetchling, and combining the Myrmidarch archetype with Dark Sight is just broken. You still will probably find a more powerful build using Oracle or Sorcerer, however.
Monk: There are no Charisma-based Monk archetypes (unless you count Ninja) and so this will always be a sub-optimal choice for a fetchling beause you’re going to start with fewer ki points. You can offset this significantly, however, by taking the Hungry Ghost Monk archetype, which will allow you to regain ki points when you confirm a critical hit or knock out a creature. You could also pick up a Monk Vow or two, so this isn’t the worst class for a fetchling.
Oracle: Now here is a great class for a Fetchling. You get a +1 to your caster level with shadow spells, and the Dark Tapestry mystery fits in perfectly with your shadowy theme. The favored class option for a fetchling Oracle is incredible, allowing you to be treated as a higher level for the purposes of which of your racial spell-like abilities you can cast. This means that you will be able to cast shadow walk (or displacement) at 7th level instead of 9th!
Paladin [Antipaladin]: A lack of a Strength or Con bonus means you’re not going to be a great front-line Paladin, but a ranged Paladin build such as the Holy Gun is definitely an option. Paladins aren’t the most sneaky class out there, but an Antipaladin could actually work out really well, especially with the fiendish servant being used as a sneaky little scout.
Ranger: Rangers aren’t affected too much by a Wisdom penalty, and obviously the Dexterity bonus lends to a ranged build. You also have the option of taking a racial archetype, the Dusk Stalker, which gives a huge boost to favored terrain when on the Shadow Plane and replaces hunter’s bond with several shadow-focused abilities. You also get the see in darkness special ability at 12th level, which is excellent. By now I’m sure you’ve figured out that i’m a huge fan of the Skirmisher archetype as a great spell-less Ranger variant, so I also recommend that for a fetchling Ranger to further reduce your reliance on a high Wisdom score.
Rogue [Ninja]: Fetchlings were practially made to be Rogues and Ninjas. All of their racial traits help with sneaking or infiltrating, and the Spy and Burglar archetypes both work perfectly along with that (and a Ninja can even take the Burglar archetype too!). The favored class option is also excellent, boosting your Stealth and Sleight of Hand checks when in dim light or darkness. You may want to consider the Gloom Strike feat, if you’re willing to spend a feat on Blind-Fight as a prerequisite.
Sorcerer: This is a really great option for a fetchling. Obviously you’ll want to pick up feats that help with your illusion spells, and the Umbral bloodline is definitely the best choice, though the regular Shadow bloodline would be fine, too. The favored class option is nice, letting you increase your innate energy resistances. Overall, this is an excellent choice.
Summoner: Of all the classes you could choose, I think this one is the best, thanks to the racial archetype available to fetchling Summoners, the Shadow Caller. This archetype gives you a lot of really interesting options for your summon monster spells, some of which are quite powerful (Young Umbral dragon!). You also get to add the shadow creature template to creatures instead of celestial or fiendish, which is really powerful. I also absolutely love the roleplay value of having your eidolon literally coalesce from your own shadow. You’ll absolutely want to give your eidolon Shadow Blend and Shadow Form, which will give it concealment at all times! The favored class option is good, letting you get some energy resistance on your eidolon without spending mutation points on it.
Witch and Wizard: Both Witch and Wizard are fine options for a fetchling, though definitely not optimal. There’s nothing that says you can’t go for it, though!
Racial Favored Class Options:
Oracle: This is a seriously excellent favored class option, letting you cast your higher-level spell-like abilities earlier. You won’t want to choose this anymore after level 9, though, because after that it wears out its usefulness.
Ranger: If you’re planning to hang out in the Plane of Shadow, such as if you went with the Dusk Stalker archetype, then you’ll definitely want this favored class option... otherwise it’s useless.
Rogue: This is a must-have for either a Rogue or Ninja, as you’ll be making a lot of Stealth checks in areas of dim light.
Sorcerer: Increasing your energy resistance is useful, though I probably wouldn’t spend all 20 levels on a single type of resistance.
Summoner: Anything that lets you save evolution points for other, stronger abilities is great in my book. Take this, and match your shadow eidolon’s resistances to your own!
Wizard: This is a super trap, as you can just buy scrolls and add them to your spellbook, and it’s even more restrictive than other racial options that allow you to add spells to your book. Stay away!
Dusk Stalker (Ranger): This is a flavorful archetype, though it will only really be useful in certain types of campaigns (such as those where you travel between planes a lot!) I do like the Shadow Bond ability a lot, and the Dark Sight class ability is more powerful than the Dark Sight line of feats, though you have to wait a while to get it. Definitely take the favored class option of +1/2 to Perception and Survival on the Plane of Shadow at every level if you take this archetype.
Shadow Caller (Summoner): I love this archetype, because it’s so full of flavor that it hurts, and it’s also very powerful! The new options on the summon monster lists include a lot of great options, though you’re also more restricted in which creatures you can summon. Adding the shadow creature template instead of celestial or fiendish to your animal-type summons is an excellent change, and I also love the two evolutions that were written with the fetchling in mind, Shadow Blend and Shadow Form. You’ll probably want to focus on Stealth and sneaking with your eidolon. I really wish you could combine this archetype with the Master Summoner, but alas they both change the eidolon class feature.
Dark Sight: This is an excellent feat, letting you see through magical darkness up to fifteen feet, but it does have a downside: you have to take the Gloom Sight feat first, which includes the light sensitivity weakness. For a ranged build, it’s likely worth it to take both of these feats, and just make sure that you keep a darkness spell up to save yourself from bright lights as much as possible.
Improved Dark Sight: This is a huge upgrade to Dark Sight, except that you now have the light blindness weakness, and that’s a really big penalty. You can always help that by wearing Lenses of Darkness, though this is an expensive solution. I would definitely not take this feat until you can afford the lenses, personally.
Gloom Sight: Increasing your darkvision to 90 feet really isn’t worth it when you also have to gain light sensitivity, but this feat is made much better by the feats that require it, Dark Sight and Improved Dark SIght. By itself, this is a bad choice, but it’s worth the investment to get to Dark Sight, in my opinion.
Gloom Strike: Blind-Fight can be a very useful feat for martial characters, and you’ll probably always want to be in an area of dim light or lower anyway, so you might as well grab this if you’re willing to spend the feat on Blind-Fight first.
Shadow Ghost: If you like your shadow walk spell-like ability, grab this, but honestly I don’t think it’s worth a feat.
Shadow Walker: Dimension door is more powerful than shadow walk, but this probably isn’t worth a feat for most characters.
Unusual Origin: I'm struggling to see a use for an arcane eye on the shadow plane. I guess you'll have some warning if shadow baddies want to attack you? Really, I think this would just encourage your GM to use such tactics.