After hearing a rumor that the Crystal Empire has returned Chrysalis set off to find it. When she gets there, however, her past with the Crystal Empire and its citizens causes some trouble for the current rulers of the Empire.
Everypony has their own inner demons they must fight, but for Twilight Sparkle hers is very real. After using dark magic Twilight learns of a powerful, and evil entity that has been sealed away inside of her, and now that she knows it's become active. Now she must learn to control it's power before it's power controls her, and it takes over her body.