Nightmare

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 * Emerald Nightmare, the corruption within the Emerald Dream.
 * Nightmare (quest), a Twilight Highlands quest.
 * Nightmare (pet battle ability), a pet battle ability.
 * Nightmares, a story in Legends Volume 5.
 * Horses connected with the name nightmare:
 * Felsteed
 * Dreadsteed
 * Warforged Nightmare
 * Lucid Nightmare