The The Crystal Empire Part 1-2.The The Crystal Empire Part 1: Princess Celestia learns of the return of the Crystal Empire, which had disappeared over a thousand years ago as the last act of King Sombra before his banishment; Celestia fears Sombra will return and use the power of the empire to take over Equestria. She summons Twilight and directs her to join her friends, Princess Cadance, and Shining Armor at the empire to help protect it as a test of her abilities. At the empire, Cadance attempts to maintain a spell to prevent the shadowy form of King Sombra from entering. Twilight and her friends talk with the residents of the empire, the Crystal Ponies, and learn of a Crystal Fair which used to enlighten the hearts of the empire and protect it from the king. But then, Twilight realize that the missing Crystal Heart is the centerpiece of the fair and a necessary artifact to protect the city.
The The Crystal Empire Part 1: With Cadance's magic weakening, Twilight instructs her friends to continue the fair to raise the spirits of the crystal ponies while she goes to look for the Crystal Heart by herself, assured this is the test Princess Celestia alluded to; however, she allows Spike to come long. The pair pass several traps King Sombra had placed in the castle and eventually come to the Crystal Heart, just as Cadance's magic gives out and Sombra races to reclaim the empire. Twilight moves to recover the heart but walks into a trap, telling Spike to take the heart in her place. On his way down, Spike falls, but he and the heart are saved at the last moment by Cadance and Shining Armor. The Crystal Ponies pour their emotions into the heart, recreating the protective spell on the empire and obliterating King Sombra. Twilight returns to Celestia, convinced she has failed her test, but the princess tells her that she has passed, knowing when to give up her personal goals for the greater good.