Things have been odd for the brother of the angel who saved the world from the Underworld army. First the Mirror of Truth is stolen from the Labyrinth of Deceit, then his unicorns Phos and Lox start acting weird. Things take a turn for the worst when he finds himself trapped in a world of magical ponies and turned into one himself!

With the Mane 6's help, Dark Pit must recover the missing mirror shards if he's to return home and get away from this "nightmare".