You must kill:
How would you feel about paying a visit to the General? No illusions, this time.
Ceremony? A pretty word to describe the bloodletting that amuses the Black Dragonflight.
All this amulet requires is the blood of General Drakkisath. Primitive security. There are other ways to receive the General's blood.
Go to Blackrock Spire and kill Drakkisath. Return with his blood and I will activate the key to Onyxia's lair.
I don't think I need to tell you that Drakkisath is not to be taken lightly.
I let the thousands dead by his hand do the talking.
You also need to kill General Drakkisath to complete the quest. Be sure to pick it up before taking on Drak to prevent having to get him again.
This quest was a part of the Onyxia's Lair attunement chain.