Nightmare Moon won a thousand years ago, plunging Equestria into perpetual night. Now, as Princess Luna's student, Twilight Sparkle must contend with Celestia's unexpected return as a familiar group of ponies are thrown into conflict.
A traitorous spy. An amoral archaeologist. A cloudheaded Wonderbolt. A secretary in way over her head. Leading them into the changeling hive is Princess Luna. There will be no going back. And none of them are prepared for what they'll find there.