Plot twist. Nightmare Moon, the evil alicorn previously mentioned a thousand years earlier, hadn't just tragically defeated Princess Luna all those years ago. No, she was Nightmare Moon! At least, the book stated she was corrupted by an evil spirit calling itself Nightmare Moon. Either way, she was somehow restored to sanity by Celestia's newest student, a young but magically gifted mare named Twilight Sparkle. In fact, Twilight featured prominently throughout the book's final chapter, including the return of the Crystal Empire, which he took particular interest in. 