"Half of the pony's pelt was dark white, the other pitch black. Her mane and tail were flowing in both directions, one liquid white, the other liquid purple. But when she opened her eyes I recoiled. One eye was fiery gold, the other slitted teal, and she spoke. She spoke with the voice of both Celestia and Luna. 'We are Nightmare Eclipse.' She yelled, her voice echoing through the castle. Nightmare Eclipse turned her head to me, and smirked. 'And you, must die.' "
The princesses have been corrupted, turned into a monstrosity, and all of Equestria has been poisoned by the Nightmare Energy. Now everyone is darker, eviler, and much more powerful. All but those select few who avoided it, and all this done by one unicorn named ShadowBright. Now she must quest to save the world from the Nightmare'd princesses, but she couldn't defeat them on her own before, how could she defeat them now that they have the Nightmare Energy on their side, even with help?