Bartemius Crouch Junior, or simply Barty Crouch Jr (known as Mad-Eye Moody in disguise) is the central antagonist in the book and the film Harry Potter and the Goblet of Fire.
He is an extremely dangerous and loyal Death-Eater and servant of Lord Voldemort, who actually disguised himself as Alastor "Mad-Eye" Moody during Harry Potter's fourth year at Hogwarts. The reason for this disguise was to lure Harry into Little Hangleton Graveyard in order to use his blood in the resurrection of Lord Voldemort. He was the one who made Harry a Triwizard champion. He was the son of Barty Crouch Senior and was the one who murdered him.