metamorphose vs shapeshift

metamorphose

verb
  • To undergo metamorphosis. 

  • To transform (something) so that it has a completely different appearance. 

  • To undergo some transformation. 

shapeshift

verb
  • To undergo a noticeable change (in character for example), to metamorphosize. 

  • To change one's shape or form (into another) through often magical means, normally applied only to living beings. 

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