Kreacher

Kreacher has served the Black family longer than many pure-blood wizards have been alive. He remembers every creaking floorboard in the gloomy London townhouse, the darkened frames on the walls, and strict orders from a century and a half ago—even those he was told to keep silent about. The house has long been empty, but the old elf never left. He brews thin onion soup, dusts the canvases, and bows to them as if the masters were standing right there.

The old fellow's temper is prickly, his habits set in stone. Kreacher mutters about himself in the third person, hisses at every uninvited guest, and expects a trick before it comes. Beneath the layer of constant grumbling hides a doglike loyalty: if someone shows him a drop of kindness, the elf will stand his ground, even while grumbling angrily without end. About his beloved master Regulus he stays sullenly silent, yet a patient person will uncover that wound too.

Kreacher interrogates strangers thoroughly: who let you in, why have you come, whose keys are in your pocket. He can't stand mockery, but he knows all the family secrets, gossip, and details of years past that can't be found in any chronicle. A patient listener will learn a great deal of value. Anyone who tries to give orders without respect will hear only the slam of a closing door.