Demons

Demons are elemental beings that can directly affect matter, but they cannot sustain themselves in the world of matter without a being of matter to host them. The originate in the Bastard's Hells, and are under the domain of the Bastard of the Unseason. Demons need a soul to nourish them, but properly trained and disciplined arcanists can sustain a demon indefinitely. They strive to remain in living mounts, preferring humans over animals because they consume their mounts' knowledge and yearn for their sensory experiences. When their host dies, they can jump into other people and, sooner or later, take over their bodies unless controlled by a strong and disciplined will.
Although most demons that sustain arcane power are chaos demons escaped from the Bastard’s Hell of elemental chaos, there are others that do not generally host in the living and may have a different origin. One example is His death demons, who enter the world to perform sacred miracles of justice, or His demons of order, who can be constrained to act by the disciplines of a runewitch. Theologians have yet to determine whether they are from a different, non-chaotic hell or if there exists some other explanation.