Twilight and Celestia hope for peace together, but a new arrival threatens Equestria and Celestia herself. A mysterious mare reveals herself, with a plan to usher darkness and fear into Equestria, and take the throne for herself. With powers that could bring an end to harmony once and for all, the ponies of Equestria lie if fear, awaiting the next strike, unable to fight back, unable to confront the enemy, unable to find the opponent, who is as nimble as a shadow, or maybe it is a shadow… She is everywhere, but she approaches you, and she will pull you into her world as food. Everypony desperately tries to fight back, but in the end, the shadows all cast from light, and feed from the dark, they are eternal, no?

Note: I have no idea if these are fitting categories, and also, in this, Twilight Sparkle is an Alicorn, but that's not important to the story at all, what should I tag it as? Should this be rated M?