Celestia, and Twilight are in canterlot one day to catch up. And they come across something they never could have dreamed up of. As well they will learn that monsters don't just happen, There's reasons that their bad.
One fateful morning, Princess Luna finds Celestia has turned into a megalomaniacal tyrant with one clear goal in mind: to be sent to the moon. She even has her bags packed and everything.
Thirsty for vengeance against Queen Chrysalis, Shining Armor leads an army south to deal with the Changelings. Prince Blueblood schemes for absolute power in Canterlot. And in the black north of Equestria, an ancient terror threatens to destroy all.