Goetia

Goetia is a practice that mages use that summons the vices of their minds into a physical form, in the belief that it will make them possible to subdue, or even destroy. Quite often, however, a Goetic mage will summon an "inner demon" that is too powerful for him to defeat, and it will escape, or even take control of the overconfident mage. Needless to say, these creatures are hunted down at all costs.