Twilight and the Elements tracked down King Sombra's horn, intent on putting an end to Sombra's threat once and for all. But when the horn is stolen, the ponies find that one of Sombra's secrets has returned, bringing hate. And in exploring the dark secrets of Sombra, the ponies find a way to resurrect the Spirit of the Rebellion, which they thought Sombra had crushed a thousand years ago.