The Gravesworn
Importance:
The Gravesworn is an armored figure that has shadowed the King's Hand since their first mission, never named by anyone who survived meeting it and never once heard to speak. It fights in dark plate, carries Dragon's Bane, and commands the dead. It first appeared in the Veiled Ravine, where Raynere Falkrest made camp with his soldiers and knew before the light failed that something was wrong. He was the only one to come out. The Sentinel of Ederia had been beaten, mutilated, and sent home alive, which made him a message rather than a survivor.
Since then
Give me the phylactery and you will live.