Serious Black introduced in the 3rd part of HP serious that is Harry Potter and the prisoner of Azkaban, was a pure-blood wizard, is also known as Padfoot.Sirius was the last remaining heir (resident) of the House of Black, a once-notable pure-blood wizarding family. He rejected his family's pure-blood elitism and reverence for the Dark Arts. At the first he appears to serve The Dark Lord Voldemort but later on after the truth revealed he became the God Father of Harry.In the beginning he was prisoner of Azkaban because he helped Lord Voldemort to kill Harry Potter and his family.At the Azkaban he saw a picture of Ron Weasley with his pet Scabbers who is a rat. Then he escapes from Azkaban by transforming him into a dog because he recognises Peter Pettigrew in his Animagus form.Towards the end of Prisoner of Azkaban, Harry, Ron, and Hermione confront Sirius and Harry attempts to kill him. Proff. Lupin, however, who has learned that Sirius is innocent, prevents Harry from doing so. Scabbers is unmasked as Pettigrew, and Harry begins to view Sirius as a surrogate father.Pettigrew escapes and Sirius is captured by the Dementors at Hogwarts and sentenced to the "Dementor's Kiss". Harry and Hermione help him escape with Buckbeak. In Harry Potter and the Goblet of Fire, Sirius advises Harry on how to complete the Triwizard Tournament tasks, and provides background on Death Eaters.