Character from harry-potter-deathly-hallows by
The Gryffindor ghost -- Sir Nicholas de Mimsy-Porpington, who once told Harry that ghosts are imprints of departed souls who were too afraid to move on, a conversation Harry remembers when deciding whether to come back from King's Cross.
Nearly Headless Nick is Gryffindor's resident ghost, and in earlier books he explained to Harry the crucial distinction between ghosts and the truly dead: ghosts are people who were afraid to move on. They chose a pale imitation of life over whatever comes next. This conversation becomes deeply relevant in Deathly Hallows when Harry faces his own death. When Harry walks to the Forbidden Forest, he doesn't become a ghost. He goes to King's Cross and comes back. Nick's earlier words frame the choice: death is not the end, but clinging to life out of fear -- as Voldemort does through Horcruxes -- is the real tragedy.
A ghost -- translucent, pearly-white, wearing a doublet with a ruff that fails to hide the fact that his head is nearly severed, hanging on by a thin strip of ghostly skin. His head wobbles when he talks.
Also known as: Nearly Headless Nick, Sir Nicholas, Sir Nicholas de Mimsy-Porpington, Nick