Long ago, the Monster-Ponies and Ponies fought a great war. The Monster-Ponies lost, and were sealed in the UnderEquestria. It would take the power of six pony souls to break the barrier that kept them imprisoned. But one escaped. Flurry Heart, who sealed away the Mane 6, in hopes that the king of UnderEquestria would kill them so the Monster-Ponies could escape.

Now with The Mane six locked away, They meet a Flower-Pony. What could go wrong.