The Statue of Death gives you 30 of these in the Empyrean citadel after the Missing, Presumed Death quest and they can also be received as a reward in the Barrows minigame.
Uses:
Used on a Barrows brother sarcophagus to kill them before they wake. You can only use a maximum of three of these on a Barrows run.
Notes:
The amulets received from the Missing, Presumed Death quest are not tradeable, while the amulets received from the Barrows minigame are.