Starlight Glimmer is victorious in stealing everypony's cutie marks. But a mysterious and creepy filly is immune to her magic. While Starlight searches for a way to beat the filly, one thing is clear...there's something wrong with that girl.
A mirror universe, where Nightmare Moon and her friends fight to protect the Everfree Kingdom. A powerful foe plots her revenge. Will Nightmare and her friends be able to defend their home?