The Elements of Harmony are not the only great power in Equestria. Long ago, the various kingdoms forged their own defenses against invaders... and at times, against each other.
An age of peace is upon Equestria though and such devices are no longer needed. But to forget the past is to repeat the same mistakes in the future, a crime almost as unforgiveable as to use these weapons out of malice. However, the peaceful are not the only ones who remember these dark powers. And they are about to be reminded yet again...