Harry Potter and the Prisoner of Azkaban attacked by a big black dog, which Harry has seen several times before. The dog drags Ron through a tunnel under the Whomping Willow into the Shrieking Shack. Harry and Hermione follow, and there is a brief standoff when they find Ron with Sirius Black, who has transformed from the dog. Lupin enters, and they explain the situation to Harry and his friends: Lupin is a werewolf, which led to his friends James Potter, Sirius Black, and Peter Pettigrew becoming animagi. Lupin explains that Scabbers is Pettigrew in his animal form; he has been hiding from Black, whom he had
Magic in Harry Potter a central authority by law, though a number of characters are revealed over the course of the series to have remained unregistered illegally: James Potter, Sirius Black, Peter Pettigrew and Rita Skeeter. Animagi transformation can be performed wandlessly. Sirius and Peter are left wandless for over 10 years, but both retain the ability with no apparent ill effects. When Animagi transform, they take on the appearance of a normal animal. However, in "Harry Potter and the Prisoner of Azkaban", it is noted that Ron's pet rat Scabbers (later revealed as Peter Pettigrew's Animagus form) has lived over twelve years when