Zero has been looking for the ponies that were responsible of the destruction of his msater and he ends up in Canterlot in need of information involving the Elements of Harmony.
He hears of Princess Luna that was Nightmare Moon and now he's goin to change her back and with him by her side she will fulfill her goal of making it might forever.
But first things first, Zero and Nightmare Moon have to take care of business in Ponyville....