We all know the song; "First comes love, then comes marriage, then comes a baby in a big fat carriage!" Except, Celestia skipped the marriage part.

Three years after her defeat, Nightmare Moon has risen to power again, followed by a brainwashed army of Equestrians, and an army of undead, ghost-like ponies. Since Celestia is unfit to battle, she leaves the burden to her younger sister, Princess Luna.

Meanwhile, the secrets of Equestria are unraveled to Princess Cadence and the Elements of Harmony.