There are some types of evil that are not easily recognizable as such. Much like the mountain-top ascetic or the cloistered saint, there is no obvious sign of the darkness that lurks inside Vodai.
A family of semi-retired doomsday cultists, just trying to live a quiet life while tending an apple orchard in the country. Except with complications.
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.