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.
The massive blade known as Consequences carries several potent enchantments of battle, but also has a frustrating quirk: Its wielder finds himself unable to put it down until he enters the presence of a magistrate or other authority. Even then, it instantly returns to his hands if he has committed murder and fails to confess. Unless he somehow resists the blade's magic, the weilder's hands then run with fresh blood; the judgmental blade fights his every motion until he confesses his crimes.