Sombra's Shadow Army and Chrysalis' Hive Forces have taken over Canterlot Castle, forcing the Princesses to retreat. Their final plan of action falls on the Harmony Orbs: magical conduits of power connected to the primal Zords: the slumbering guardians of the planet.
Princess Luna has located the town of Pony Grove, where the Orbs had chosen the worthy bearers of the powers of good.
These chosen people will then defend against the impending armadas to prevent the doom of the Earth...