You walk into the room and it is like stepping into the grand library. Wall to wall and floor to ceiling is taken up by leather bound loaded bookshelves. All of the tomes are in varying states of decay and none of which are new.
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.