1) Belief in demons 2) Belief in genii, etc 3) Black art 4) Black magic 5) Demonology 6) Diabolism 7) Necromancy 8) Satanism 9) Sorcery 10) The study of demons Found on https://www.crosswordclues.com/clue/demonism
De'mon·ism noun [ Confer French démonisme .] The belief in demons or false gods. « The established theology of the heathen world . . . rested upon the basis of demonism .» Farmer. Found on http://www.encyclo.co.uk/webster/D/34