Peter Pettigrew

Peter Pettigrew, also known as Wormtail, was a friend of James Potter, Remus Lupin, and Sirius Black.

Pettigrew was a member of the Order of the Phoenix, but he was working as a double agent for Lord Voldemort. He was appointed the Secret-Keeper for James and Lily Potter and betrayed them. Once they were killed and Voldemort destroyed, he went into hiding as Scabbers the rat, coming into the possession of Percy Weasley and, later, Ron Weasley.

In Harry Potter and the Prisoner of Azkaban, Pettigrew was unmasked by Sirius Black and Remus Lupin, but escaped being handed over to the Dementors. He returned to the service of Lord Voldemort and was later assigned to "assist" Severus Snape &mdash; which Snape interpreted as Pettigrew being his servant.