Rivals

         Without enemies, heroes are just people.  You likely already have a "BBEG" (Big Bad Evil Guy), or main antagonist, the character who your players are supposed to stop.  He's either already in the adventure path, or he's a main fixture in the campaign you have designed.  However, you can spice up your game by including Rivals into your story.  There is one Rival for each PC, and this Rival will encourage roleplaying, further invest the player in the plot, and expand on the character's backstory.

Designing Rivals

         Each of your player character's should have one (and only one) Rival.  The Rival is specific to them alone and should be drawn from the PC's past.  The Rival should already have a connection to the PC, so when he shows up in the game only the PC (and nobody else) will know who he is and why he is there.

         Rivals should be the central fixture in a PC's backstory.  If the PC's parents were brutally murdered, then perhaps the Rival is the murderer.  If, on the other hand, the PC has lead a life of crime, then perhaps the Rival is the widow of a victim, here to get revenge.  The PC is the last remaining member of an organization or race?  Perhaps the rival is, for one reason or another, dedicated to exterminating them from the planet.  Or, perhaps, the PC is not as alone as he once thought..

         Family members (even evil twins) make excellent rivals.  Their connection with the PC is strong and family bickerings make for great roleplaying and storytelling.  It also ups the PC's desire to redeem his rival.

         Rivals should generally be the same class as their PC counterpoint, for three reasons.  First, the more similar the Rival is to the PC, the better "foil" or counterpoint he presents.  Second, when the Rival is overcome, the loot he will drop will be directly applicable to the PC.  Third, it's just more fun that way!

         When fleshing out the Rival's backstory, have his personal story be tied up with a preexisting aspect of the campaign BUT NOT WITH THE BBEG.  At least, not yet.  The point of Rivals, at first, it to flesh out one PC's backstory and personality apart from the main plot line.  However, regardless of what aspect you place the Rival into, his desire to crush his PC MUST be his primary objective.  If the Rival is the bodyguard of a King, the Rival's job as a bodyguard will come second to his desire to destroy his PC.

         Lastly, all Rivals must be separate and distinct.  They should all have different personalities, and none of them should know each other.  Most importantly, all Rivals should be equally important to the main story line - not very much at all (to start).

Introducing Rivals

         The first actual appearance of the Rival into your game can be done in any number of ways.  He can simply surprise and attack the heroes in their travels, shouting his motivations along the way.  A long game of cat and mouse can end in a confrontation.  The Rival's PC may know he is coming, but not inform the rest of the group.  Or, perhaps best of all, the Rival can be there all along, but his existence as an antagonist only manifests itself in a shocking betrayal (this works best with family members).  As mentioned before, all Rivals should be very different, and so they should be introduced in different ways and at different times.  While one Rival might be introduced in the first session, another Rival might not be introduced until session 15.  However, all Rivals should be introduced before the halfway point, to give them all proper time to be fleshed out.

         In any case, the most important part of introducing Rivals is to let the PC do the explaining to his companions.  When the Rival appears, simply describe him as the ignorant PCs see him.  If the Rival's PC chooses to explain, then let him.  If the PC wants to keep quiet or leave some things out, perhaps due to character shame or guilt, then that is his prerogative.  A Rival is each PC's personal slice of the story, and the PC should have a great deal of say in what happens to him.

         When introducing Rivals, remember that they should be about the same level as the heroes (or, if a solo encounter, a few levels higher), but far weaker than the BBEG.  Rivals are people too, and should not feel like omnipotent gods.  They can be overcome, and they will be.

Evolving Rivals

         The Rival will, of course, escape from the first encounter.  The next time the heroes meet the Rival, he will be bigger, stronger ... but also more entwined in the main story line.  As our heroes learn more, so do the Rivals.  Our heroes are collecting artifacts?  Perhaps a Rival has acquired one. Perhaps two rivals have met, and are now working together.  Perhaps the Rival has taken up the same quest as the heroes, but is pursuing it for his own nefarious purposes.  Or, perhaps his first failure has filled him with one, all encompassing desire:  kill the PCs.

         The Rival grows more and more obsessed with destroying his opposite.  However, since the entire party likely had to band together to take the Rival down, he will also learn to hate the party as a whole.  This process, of taking one character's problem and distributing it amongst the group, is crucial to character and party growth.  However, the Rival's primary objective should always be his original PC.

         Remember, always keep the Rivals distinct from the BBEG.  All Rivals should be weighed equally, and if one take the place of the BBEG's right hand man, the Rival system falls apart.

Finishing the Story

         There are three main ways to close the loop on a rivalry.  First, each Rival can be picked off one by one.  A climactic fight, just like the ones you have been doing before with the entire party versus one Rival at a time.  Make it obvious that this is the Rival's last incarnation.  He won't escape again - it's kill or be killed.  Try and ensure that the original PC get the final blow, whether this means fudging the rolls or designing the battlefield so that the final portion of the battle is just the PC versus the Rival.  In general, you don't want to have fights that exclude some PCs, but this is a fine place to make an exception.  The rest of the team will be rooting the Player on, if you have built it up enough.

         A second, more entertaining method, is to have all the Rivals band together.  The final, climactic Rival fight is the entire party against the entire party of Rivals.  It's particularly fun because each Rival is the same class of his opposite, making this a nice mirror image duel.  Also, PC's will inevitably single out their Rivals, so tensions will be high.  However, it can be a bit strange trying to find a reason for the Rivals to band together, so make sure you either have a good reason, or make sure the fight is so awesome that the PC's don't mind.

         The third method is to have the BBEG step in.  At the end of the campaign, the BBEG should be visible, dangerous, and aware of the players.  The Rivals could (all of them or none of them) act as the BBEG's henchmen.  Or, more interestingly, the BBEG could actually kill the Rivals!  This is a nice way to transfer your hatred of the Rival to the BBEG, given that the player probably wanted to either kill or reform the Rival himself.  And if the Rival had earned the begrudging respect of the group, it will be all the worse when the BBEG takes him out.  However, the problem with the BBEG killing the Rival is that he should do it to all of them, or he should not do it at all.  And this kind of twist is best used once, so the BBEG must kill all of them at once.  It could also be cooky to orchestrate that.

In Conclusion...

         In any case, Rivals add a lot to the game.  They develop individual's characters stories, attach the character's story to the larger plot, and bring the group together.  They also add some memorable NPCs!  Just remember - favor each of the Rivals equally in terms of attention, make sure sure that each Rival is distinct in character!