Alastor "Mad-Eye" Moody, Defense Against the Dark Arts teacher in the fourth book, is a retired Auror, supposedly obsessed with catching Dark wizards. It is said that half the cells in Azkaban are full because of him. He was forced to retire when he became too paranoid of attack. He helps Harry to get through the tasks of the Triwizard Tournament, acting like a friend the whole time. The reason for this is discovered when, at the end of the school year, it is discovered that Moody was never really the teacher, but that he was Bartemius Crouch Jr. using Polyjuice Potion to appear that he was Moody. Bartemius Crouch Jr. was a former prisoner of Azkaban, arrested for being caught working for Voldemort, who was supposed to be dead. Under the influence of Veritaserum, he reveals that his father sneaked him out of Azkaban, replacing him with his mother, who used Polyjuice Potion until she died not long after. He also reveals that he had been the one who put Harry’s name in the Goblet of Fire, turned the Triwizard Cup into a Portkey, and helped Harry through the tasks so he would meet up with Voldemort, which would help bring him back to full strength. After he had given Dumbledore all his information, he had the Dementor’s Kiss performed on him, a fate which many believe he truly deserved.