the conjuring up of the spirits of the dead in order to predict or influence the future
magic or sorcery generally
necromancer noun
necromantic /-ʹmantik/ adj
necromantically /-ʹmantikli/ adv
[Middle English nigromancie, via Old French from medieval Latin nigromantia, an alteration, by folk assocation with Latin nigr-, niger black (hence sense 2) of late Latin necromantia, from Greek nekros corpse + Latin -mantia -mancy]