The Lucid Nightmare is a dark unicorn mount.
This item is looted from the Puzzler's Desire in the Pit of Criminals in the Forgotten Crypt. This mount is the reward of the Riddle of the Lucid Nightmare. It starts with an Inconspicuous Note in Curiosities & Moore at Dalaran above the Broken Isles.
When riding this mount, your thoughts often wander to far-off places.