It shouldn't have happened. Portals from another universe open up like rifts and tears as from forth pour out the Heretic, the Xenos, and the Mutant.

Twilight, her friends, and all of Equestria have no option but to align themselves with the Imperium as the forces of all other races assault their precious boundaries around Canterlot, Ponyville, Sweet Apple Acres, and the Crystal Empire. They must cast aside their ways, take up arms alongside the newly transformed Imperium, and fight back the evil tides that threaten everythings way of life.