Sombra may have been defeated after his attempt to retake the Crystal Empire, but he was not destroyed. He still lives, and now he seeks to work his way into the mind of Princess Twilight Sparkle. As she struggles with the implications of her new immortality, she finds less comfort in the wise words of Princess Celestia, and is drawn to the dark magic of a fallen king.

1000 years ago lived Starswirl the Bearded. The greatest unicorn magician at the time, and the personal student of Princess Celestia. In his study into the nature of magic, Starswirl finds a spell unlike anything the world has ever known. Unfortunately for the old unicorn, casting this spell turns his entire world upside down and sideways and brings the elements of Harmony down along with him.