After being a secret society for several decades, the Shadowbolts are revealed to be real, and a military force rivaling Equestrian forces, led by a corrupted Lightning Dust.

In a surprise attack, the Shadowbolts attacked and captured Cloudsdale, and are planning to target Ponyville, as the many farms there help supply the Equestrian population with food.

Cloudsdale has only been captured moments before the advancement to Ponyville, so nopony knows about the invasion yet.

Meanwhile, a middle-aged unicorn has decided to move to Ponyville. Lance Corporal was the Captain of the Royal Guard for thirteen years before passing the position to Shining Armor, who had shown great promise.

Since then, Lance has lived in semi-retirement, working as a personal servant to the two princesses, as well as becoming a close friend to both. After a few years of this, he has gone into a full retirement, and just moved to Ponyville, right as the Shadowbolts plan to launch a massive invasion on the small town.

Just as Lance settles in, a surprise party thrown by Pinkie Pie and the other Mane Six members in interrupted by a Shadowbolt and Wonderbolt battle in Ponyville.

All Lance wanted was to begin a new life, but now he has to help Ponyville fight a war to stop the Shadowbolts.