An eccentric former Auror -- dark wizard hunter -- convinced by Hogwarts' headmaster Albus Dumbledore to teach Harry and his schoolmates how to defend themselves against the dark arts.

Moody is so paranoid that he only drinks out of his own hip flask. And he has good reason to be so: He is responsible for many a Voldemort follower being killed, or sent to Azkaban, the wizard prison.

He gets his nickname from a magical eye that can see through solid objects and even behind him, and which he got after losing one of his own in the line of duty.