So this weekend I'm starting my group on the next arc of the campaign. The current plan is to have them go after this "evil wizard" they keep hearing about (one of the characters claims that the wizard has her possessed). I'm thinking I'll have them go through different dungeons and stuff trying to find information about this guy's location, until they finally find him and confront him. The catch is, the name they're chasing is actually that of a nice guy, and the evil guy is just using it for some evil purpose reason.
The problem is, I need to design the villain now so that I can have him start moving against the PCs (in a behind-the-curtain, mastermind sort of way). So I'm looking for ideas. I'm considering the idea that he rules over an area of the map for some reason (kinda like the standard vampire lording over his cattle scenario). But I'm not sure I want to just go with a powerful vampire. I'm considered throwing the Soul Eater PrC on something, so having him live on the local populace. Any ideas for other variants?
I'm also considering using a Rakshasa, since I've never used one and think it could be fun. But I can't really find any information about these things and what they act like (like what their goals would be). So does anyone have any info/ideas they could share?
Or just any other scenarios I can use? Or just ideas for the adventures? Thanks a bunch.