Peter Pettigrew (Wormtail)
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Affiliation: Death Eater
Pettigrew (a.k.a. Wormtail) first shows up in Harry Potter and the Prisoner of Azkaban, when Harry preserves his life, even though Wormtail is a traitor and partly responsible for the deaths of Harry's parents. As a result of Harry's merciful act, Wormtail owes Harry a "life debt," which proves to be important in Deathly Hallows. A weak and pathetic servant of Voldemort, Wormtail is one of Harry, Ron, and Hermione's jailers in Malfoy Manor. When Harry and Ron attack him, rather than killing Harry, Wormtail ends up killing himself (actually, the magical prosthetic hand that Voldemort gave Wormtail strangles him, but still).