The state or practice of being inspired by a demon or devil. (adapted from obscure word site The Phrontistery, defining "demonosopher")
demon (an evil spirit; devil or fiend, from Middle English, from Late Latin daemōn, "spirit," from Greek daimōn, "divine power") + -osophy (suffix meaning "knowledge," from Old French -sophie, from Latin -sophia, from Greek -sophia, from sophia "skill, wisdom, knowledge," of unknown origin)
The force employed by the African necromancers is not psychological action but demonosophy.
--"African Magic" by H. P. Blavatsky (Blavatsky.net)