After her cousin, Duke Blueblood, deals a successful coup and takes over the kingdom of Soothsay as its new king, Princess Rarity sells her very being to a demon.
Waking from a nightmare with no memory of what happened, Apple Bloom is shocked. She has become an Alicorn! To find what has befallen her, she seeks advice of Princess Celestia. But the royal sisters have vanished, unfurling a real nightmare!
Twilight Sparkle is Dead. Her friends decide this isn't an acceptable state of affairs and vow to change it. They really should have compared notes first.