It was only the courage of Derpy Hooves and sheer luck, or perhaps the will of Harmony, that saved Princess Twilight Sparkle from Tempest Shadow's attack. If Derpy hadn't been nearby, if she hadn't bravely jumped in the way, if she hadn't been wearing a Princess Twilight costume, or if that costume hadn't fooled Tempest for just long enough, then Twilight Sparkle would have been captured along with the other princesses.

In another world, Derpy was a little farther away and Twilight was not so lucky.

Now it is up to the other Elements of Harmony and Starlight Glimmer to fight back. They find resistance fighters where they can, gathering up royal guards who escaped the attack, desperate townsponies with nothing to lose, and even the Spirit of Chaos himself (when he's in the mood). They strike where they can, disrupting supply lines and targeting weak outposts. It is a desperate battle, and one that they seem destined to lose.

Their greatest hope lies at the heart of Canterlot, with the four captured princesses. If they can free the Storm King's captives, they'll break his power and finally have a chance to free their beloved homeland. Unfortunately, that means getting past the Storm King's army, the King himself, and the one creature who may be even more dangerous than him: The brutal, ruthless, and seemingly unbeatable leader of his forces, Commander Tempest Shadow.