Another ancient villain of old appears in Equestria after his 1000 year imprisonment and Twilight is angry because of it! Not at the bad guy, but at Celestia for failing to mentioning ANOTHER powerful, sealed away villain that managed to escape.
Starlight Glimmer finds a book in the basement of the Friendship Castle, it's unlabeled and gives off a unsettling vibe; so she ask Twilight to help study it's contents. What they find is both interesting and disturbing. But also funny!