Mephistophelean vs demonic

Mephistophelean

adj
  • Showing the cunning or ingenuity or wickedness typical of a devil. 

demonic

adj
  • Extremely cruel or evil; abhorrent or repugnant. 

  • Pertaining to dæmons in ancient Greek thought; concerning supernatural ‘genius’. 

  • Pertaining to demons or evil spirits; demoniac. 

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