necromancy

noun3

1. •
   Divination involving the dead or death.

   • And in one word for all, Nagomancy, or Necromancy; by inspecting, consulting, and divining by, with, or from the dead. — 1652
2. •
   Loosely, any sorcery or witchcraft, especially involving death or the dead, particularly sorcery involving raising or reanimating the dead.
3. •
   (Internet) Synonym of necroposting.