He was once a king of men. He was once great. His spirit was still strong, not thriving, but not dying. He was not alive, but not dead, and it was a strain. He could almost feel the chains of deceit and malice that laced his very self. He was no longer a man and he despised the great men and women that were rising from the ashes of Middle-Earth to take their places among the great. The ring he had once worn had defined his place, but he had fallen from that grace.
How he hated Sauron. He hated him with every part of him, but he was nothing but a slave to his will anymore. He knew they were terrified of him, and he cackled with an evil power, even though he also knew that he served a master whom he hated. He was the Lord of the Nazgul, and he would have given the sick pleasure he drew from killing for the peace he so deserved.
As Eowyn's arm descended down, bringing a sword with it, piercing his soul, he shrieked. The shriek was not of anger, not of pain, not of fear. The shriek was one of relief. He had been released from his oath and he was free to seek mercy from Eru for his sins.