In The Farthest Shore
After Cob had been defeated by Ged before The Farthest Shore, he went to Paln to learn dark magic. Cob then began to try to avoid death, therefore he died to create a passage between the Dry Land and Earthsea, which drained the magic of Earthsea and made him immortal. He confronted Ged and Lebannen on Selidor, where his physical body was crushed by Orm Embar. After he had faced up to Ged in the Dry Land he died because the breach had been closed.
Cob is described as a tall and long-armed man with dark long hair and blind eyes. In the Dry Land he appears with white-gray hair and empty eyeholes.