Le bijou d'amour (The Love Jewel) (1978)

Adrien is a journalist specialised on the "strange". He is asked to interview a man who is said to know succubi. He meets a woman at the cemetery's entrance who offers him a ring which had belonged to Casanova and has magic powers which enable the journalist to make his fantasies come to reality. But he must sell this ring within seven days for fear of a terrible death