Demonism (synonymous with daemonomania = possession) denotes a peculiar state of mind characterized by the fact that certain psychic contents, the so-called complexes, take over the control of the total personality in place of the ego, at least temporarily, to such a degree that the free will of the ego is suspended.
Jung provides the canonical depth-psychological definition of demonism as complex-possession displacing ego sovereignty, linking it to primitive phenomena, trance, shamanism, and epidemic psychosis.
, Collected Works Volume 18: The Symbolic Life, 1976thesis