All is now ready, $N.$B$BWhen alive, Lord Valthalak used to inhabit what is now The Beast's chamber. Go there and use the Brazier of Beckoning to summon forth Lord Valthalak. It will reincorporate him, so he'll have to be killed again. I'd take care of The Beast first, and be sure take enough friends along to survive the upper portion of Blackrock Spire.$B$BOnce you've dispatched Valthalak, use the amulet on his corpse. With his spirit reunified, he'll likely want his amulet back, as well.$B$BGood luck!