Bluebeard

noun

1. A man who first marries and then murders one wife after another.
2. The hero of a mediæval French nursery legend, who, leaving home, enjoined his young wife not to open a certain room in his castle. She entered it, and found the murdered bodies of his former wives. -- Also used adjectively of a subject which it is forbidden to investigate.
3. (fairytale) a monstrous villain who marries seven women; he kills the first six for disobedience