necromancy vs diabolism

necromancy and diabolism both are nouns.

Word	Noun	Adjective	Verb	Adverb
necromancy	Yes	No	No	No
diabolism	Yes	No	No	No

As nouns, diabolism is a hyponym of necromancy; that is, diabolism is a word with a more specific, narrower meaning than necromancy:

necromancy: the belief in magical spells that harness occult forces or evil spirits to produce unnatural effects in the world
diabolism: a belief in and reverence for devils (especially Satan)

Other hyponyms of necromancy include witchcraft, witchery, bewitchment, enchantment, demonism, Satanism, obiism.

necromancy (noun)	diabolism (noun)
conjuring up the dead, especially for prophesying	a belief in and reverence for devils (especially Satan)
the belief in magical spells that harness occult forces or evil spirits to produce unnatural effects in the world