The Arch-Library is the greatest repository of knowledge in all of Equestria. Existing since before Princess Celestia was even born, the Arch-Library has had many curators maintain its halls, but now the current curator, Iscariat Faust, faces the greatest challenge of his life. After King Sombra pilfers an ancient scroll written by the first curator, Iscariat must seek him out with the aid of Princess Twilight and the other mane six. However, things take a turn for the worst when Sombra surprises them all by kidnapping the Princess of the Night, from her own bed chamber. Just what is King Sombra planning? How does Princess Luna play into it? An will Iscariat and the others be able to stop it?