It's been three months since Applejack came into contact with Twilight, who claimed to be from another timeline. The war against King Sombra and the Crystal Empire seems to be going nowhere. Rainbow Dash, despite being a fearless commander, is having trouble with managing her feelings toward Derpy Hooves. Celestia and her best unicorns are having the worst of luck trying to find something, anything to cease this fighting and bring King Sombra to his knees.
The whole of Equestria is starting to doubt King Sombra will ever be defeated, until the Princess enlists the help of a few unlikely heroes.