The Winter of Nightmare

After being defeated by the elements of harmony, Nightmare Moon wakes up in a strange new world. Meanwhile, the Windigos and King Sombra attack Canterlot.

Nightmare Moon wakes up in a world where everyone walks upright. After being taken in by a group of strangers who are way too trusting, she starts to question her past actions. Meanwhile, in Equestria, King Sombra makes an alliance with the Wendigos.

Takes place before Twilight is an alicorn