King Ferrum of the Crystal Empire sends his sons on quest to search for the Crystal Maiden to determine the heir.

Twilight must face an ultimate, corrupting evil in the form of the Six Sinestros. Aiding her is a stallion with a deep connection to Equestria's history.

5 years has passed since Twilight was crowned princess. Having successfully rebuilt Everfree Castle and it's city, Twilight rules under Celestia and faces past enemies returned.