I was watching The Rite (2011) and this reminded me of a horror/occult book I read many years ago which was quite gripping and well written.
Unfortunately I can't remember either the title or the author, although I think it was 1980's vintage. It was about a French noble of the middle ages called Guy de Something (?) who made a pact with the devil to live forever by tricking people into speaking some kind of litany which they thought would summon the devil to give them powers but would instead allow Guy de Whatsit to take control of their minds. In return he promised his boss (the Devil) that he would find more followers for him.
The key to getting rid of him once and for all was to find his buried bones and destroy them. For some reason I remember the book described him with "shoulders as wide as an axe handle".
It could be that this character was based on the French noble Gilles de Rais as his name popped up on Google.
The film "The Ninth Gate", which I thoroughly enjoyed, has a similar theme of the devil tricking people who are keen to invite him to pay a visit but it is a different story.
Other scenes in book
- Set in France
- Early in the book, a lawyer/professional is tricked into reading the "litany" and the villain immediately takes him over
- Forced stubborn parking attendant to chew own fingers (thumbs?) off