Nightmare Keys are quest items from The Legend of Zelda: Link's Awakening. The equivalent of Boss Keys found in other Legend of Zelda games, Nightmare Keys open the doors leading to the lair of a dungeon's respective Nightmare. The key's handle is shaped like a head with horns. Since it relates specifically to the Nightmares, which are exclusive to Link's Awakening, this is the only game in which it appears.