demoniac vs diabolic

demoniac

adj
  • Of or pertaining to demons; demonic. 

  • Possessed or controlled by a demon. 

noun
  • Someone who is possessed by a demon. 

diabolic

adj
  • Showing wickedness typical of a devil. 

  • Extremely evil or cruel. 

  • diabolic magic square 

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