This story is a sequel to Doctor Whooves Episode 15: The Christmas Ponies
The Doctor, Twilight, and Derpy decide to take Donna to Equestria. However, they accidentally end up in the year 56, where Equestria is currently caught in a bloody war with the newly-founded Changeling Empire. When Derpy and Donna are taken captive, the Doctor and Twilight must team up with a hardened Celestia and a simple farmmare in order to stop the merciless Queen Esmeralda.