Queen Chrysalis and the newly resurrected King Sombra attack Equestria and kill Princess Celestia to… Give Princess Luna the throne?

Changelings are accepted into society, the Princess of the Night rules the land peacefully and the ponies have been released from the "lies taught to them by Princess Clelestia".

But behind the veil of peacefulness, King Sombra's sinister guards made of shadow patrol Canterlot, Queen Chrysalis rules Equestria through the traumatized Princess Luna, the Mane Six are scattered and the Elements of Harmony are slowly decomposing. Four unlikely allies must team up and wield the four remaining Elements of Harmony to restore true light to the land.