Being at the Equestria Games has reminded Princess Twilight about the dark unicorn they had to defeat: Sombra. Twilight knew that Sombra was evil, and that he wanted to enslave the Crystal Empire, but other than that, she knew nothing more. To sate her curiosity about the mysterious tyrant, Twilight goes to the only pony she knew who could tell her about him: Princess Celestia. Twilight was expecting a good story, but didn't expect it to include Discord and Nightmare Moon.