Luna has been locked away in the moon for fifty years. The only company she has is the darkness that swirls around in her mind: the Nightmare.
When Luna begins to loose any hope of escaping, the Nightmare Moon leads her to an alternate Equestria, where darkness and the evil rule. Once there, Nightmare Moon tells her to search for the Nightmares: eight immortal beings who rule over this odd new world. With their help, she can fully embrace the power of nightmares and bring down her sister once and for all. But Nightmare Moon has some different plans...
Meanwhile, an alternate Discord begins his plan to escape, but when he learns of Luna's posession, he will do everything in his power to stop her from succeeding.
However, after Luna trains with a few of the Nightmares, she becomes something neither Discord or Nightmare Moon managed to foresee. Something all creatures fear... Human.