When Queen Chrysalis discovers a way to separate Nightmare Moon's soul from Princess Luna, the evil pair team up with Discord to take on Equestria, plunging the peaceful world into darkness. Both Luna and Celestia start armies, one to guard the night and one to take on the day. But the two princess have very different ways of leading armies, and the Elements of Harmony must choose where their loyalty lies. Will they pick the Solar Empire or the Lunar Republic? And how will that affect the outcome of the Great War?