Literature
My Little Pony: Bad End A.U.
Discord had cleverly tricked the Villains to work together. When Sombra was "Defeated" Discord had put a spell to teleport Sombra back to "Grogar's" cave, instead of the tree of Harmony. After all, Discord knew they needed Sombra. But what he didn't know is that they were planning on corrupting Luna, and Celestia. After Discord found out they're plan, he warned the Princesses, and said he could keep them safe, even after corruption.
With Starlight, and Sunburst's help, they put a spell on both Princesses, to at least have some control over they're body, and mind. After the real plan was in motion, Discord expected Twilight, and her friends t