Twilight wakes up to find that she has lost her voice completely, and even worse, her magic. All the while, Ponyville is being absolutely annihilated by a unicorn that looks exactly like her.
Twilight Sparkle’s brilliant mind was gone, burned away by her own power when she nearly destroyed Canterlot twelve years ago. Now there is a monster prowling the Everfree. And it is starting to remember what true power felt like.