necromancy vs the black arts

necromancy

noun
  • Synonym of necroposting 

  • Divination involving the dead or death. 

  • Loosely, any sorcery or witchcraft, especially involving death or the dead, particularly sorcery involving raising or reanimating the dead. 

the black arts

How often have the words necromancy and the black arts occurred in a corpus of books? (source: Google Ngram Viewer )