Great Crystal War

The Great Crystal War is a war waged between Equestria and the Crystal Empire in an alternate timeline created by Starlight Glimmer. It is featured in the season five episode The Cutie Re-Mark - Part 1 and Enterplay's collectible card game.

Depiction in the series
In The Cutie Re-Mark - Part 1, Starlight Glimmer uses Star Swirl the Bearded's time travel spell to go back in time and stop Rainbow Dash from performing her first sonic rainboom. This sets into motion an alternate chain of events, beginning with Twilight Sparkle and her friends not earning their cutie marks.

Years later, the Crystal Empire reappears in Equestria's Arctic North, bringing the evil King Sombra with it. According to the Applejack of this timeline, Sombra then retakes control of the Empire and wages war on the rest of Equestria, using mind control helmets to force the Crystal Ponies into his army of soldiers. Over the course of the next several months, the Crystal Empire's borders expand across Equestria, including the San Palomino Desert, the Badlands, and portions of Griffonstone.

Princess Celestia and her subjects fight back against the invading Crystal Empire. The royal guards, Wonderbolts, and other ponies are enlisted into Celestia's army, serving as either soldiers or war effort supporters. Meanwhile, Princess Celestia's research mages look for a counterspell for Sombra's mind control helmets.

The Twilight Sparkle and Spike of the series' main timeline briefly visit this reality and bear witness to the effects that the Great Crystal War has had on Equestria. They depart from this timeline before the war's resolution.

Participants

 * Army support
 * Sweet Apple Factory
 * Applejack
 * Big McIntosh
 * Rarity
 * Fluttershy

Key events

 * King Sombra declares war on Equestria and uses mind control helmets to enslave the Crystal Ponies.
 * The Crystal Empire expands across Equestria.
 * The ponies of Equestria fight back against the Crystal Empire, with Princess Celestia serving as general.
 * Sweet Apple Acres is re-purposed into an industrial factory to provide food for the front lines. The Apple family starts producing sour apples instead of sweet apples.
 * Rainbow Dash joins the Equestrian army's Air Cavalry division and serves as commander. During the war, she loses her left wing, and it is replaced with a cybernetic limb actuator.
 * Pinkie Pie and Maud Pie join the army's Rock Troopers division.
 * Rarity and Fluttershy relocate to Manehattan to help with the war cause, making soldier uniforms.

Other impacts

 * Most of the alternate Mane Six have not met.
 * The Castle of Friendship does not exist; only the Cutie Map remains.
 * Ponyville is in shambles, with most doors and windows boarded up.
 * Sugarcube Corner is an ordinary bakery.