Harry Potter and the Half-Blood Prince
Kreacher is the house elf that Harry inherits after Sirius Black leaves him Grimmauld Place. Though Kreacher must serve Harry, he still holds allegiance to the Black family. He doesn't enjoy serving Harry very much, especially when Harry has him follow Draco Malfoy around. Fortunately, Dobby is around to follow Kreacher and to make sure he follows Harry's orders.