Kreacher

A house-elf who served in the House of Black, Kreacher's loyalty to the Black family was absolute and undying. He also absorbed the anti-Muggle beliefs of the Black family. When 12 Grimmauld Place was designated as the headquarters for the Order of the Phoenix, he was furious at the presence of non-Pure Blood witches and wizards in his family home. Kreacher was difficult, untrustworthy and had a tendency to hoard possessions, but as Hermione suggested, this was a result of being treated so cruelly by the Black family.