Now Sirius was grinning. "My brother Regulus, whom I thought was a Death Eater till the end, pranked Voldy. Regulus stole a horcrux from Voldy before Voldy killed him, and Regulus ordered Kreacher to destroy the horcrux. Kreacher couldn’t destroy it, but Bloodscream can—and will, today. Shit, I never realised that the reason that Kreacher has been such a berk since 1981 was that he’d been given an order that he couldn’t carry out—which to a house-elf, is hell on Earth."