Kreacher is a house-elf, and is in the service of the Black family. Kreacher is very old; his skin appears to be several times too big for him, and although he is bald, a quantity of white hair grows out of his ears. His eyes are a watery grey colour, and his fleshy nose is large and snout-like. He wears a filthy rag tied like a loincloth around his middle.
Kreacher has a tendency to prowl around the house in the early hours of the morning. Ron says that on the first night the Weasleys' stayed at Grimmauld Place, he woke to find Kreacher wandering about the room at three in the morning.
Although Kreacher is supposed to take orders from the occupants of number twelve, Grimmauld Place, he has a deep dislike of the blood-traitor Weasley family. He mutters insults about the various occupants of the house under his breath, calling the group a bunch of Mudbloods, werewolves, traitors and thieves. When he is overheard by Fred, he freezes in his tracks and gives a very pronounced and unconvincing start of surprise, then bows to the boy. He appears convinced that they cannot hear him, and continues to insult the group. His pale eyes widen when he sees Harry, and mutters that he wants to know how Harry managed to stop Lord Voldemort.
Sirius reveals that, although the house-elf claims to be cleaning, he has been hiding a hoard of items from the house in his room, to prevent them from being thrown away. Kreacher is horrified at the prospect of the Black family tapestry being removed, knowing that his mistress, the deceased Mrs Black, would have been very upset. Kreacher has a real dislike of Sirius, his master, and considers Sirius to be a traitor to his family. Kreacher doesn't think Mrs Black would be happy to see him serving Sirius, knowing how much she hated her son after he ran away. Kreacher cannot disobey a direct order from Sirius, but performs the tasks he is set reluctantly and ungraciously. Sirius refuses to set Kreacher free, as the house-elf knows too much about the Order of the Phoenix, and says that Kreacher would take the news very badly in any case. As those in the drawing room attempt to clear it of unwanted items, Kreacher continues to try and smuggle items to safety, and mutters horrible curses every time he is caught. When Sirius wrestles a large golden ring bearing the Black crest from him, Kreacher bursts into furious tears and leaves the room sobbing, cursing Sirius as he leaves. Kreacher isn't as devoted to the memory of Orion Black, Sirius's father, as he is to Walburga Black, Sirius's mother, but was caught hoarding a pair of Orion's old trousers the previous week.