hex vs the black arts

hex

verb
  • To cast a spell on (specifically an evil spell), to bewitch. 

noun
  • A spell (now rare but still found in compounds such as hex sign and hexcraft). 

  • A hexagonal space on a game board. 

  • An evil spell or curse. 

  • A witch. 

  • a hexagon-shaped item of rock climbing equipment intended to be wedged into a crack or other opening in the rock. 

the black arts

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