A commoner has run into a LOT of money! Unfortunately, everyone knows it. Good luck getting out of town in one piece!
The local lord has been deprived of his prize family heirloom, the thief isn’t exactly a thief, but rather an absent minded wizard. Get the heirloom from the kindly but absent minded professor. Simple, right? Well, except for the fine print.
All spell casters gain their abilities through a form of demon possession. So in order to gain magical abilites, PCs must track down and trap demons. Of course there are some pretty powerful demons, if the demon is stronger than the PC, the PC could find themselves subjugated to the Demon's will.