In the not-too-distant future, Equestria has been overrun by a new changeling army. Rising over the corpse of the old Queen Chrysalis, Queen Vespida and her newly enhanced army will stop at nothing to take Equestria for themselves.

But there is still hope for ponykind - Canterlot still stands, a bastion against the changeling hordes. And among the mares and stallions that defend the mountain city in it's second year of siege, there is one whom Fate has special plans for.

Rainbow Dash.