Oldest and largest of the castles of the Night's Watch, the Nightfort was the first raised upon the Wall, said to be as old as the ice itself. Too vast for the dwindling Watch to keep, it was abandoned in the days of Good Queen Alysanne, its garrison removed to Deep Lake, and it has stood empty for some two hundred years.
Dark Legends
No castle of the Wall carries darker tales. Here the Night's King is said to have ruled with his corpse-pale queen until Stark and Joramun cast him down, and here the Rat Cook served an Andal king his own son baked in a pie, for which the gods cursed him to devour his young forever.
The Black Gate
Deep beneath the castle, at the bottom of a well in its kitchens, stands the Black Gate, a door of pale weirwood old as the Wall. It opens to no key nor force, but only to a Sworn Brother of the Night's Watch who speaks the words of his vow.