In order to fully understand the situation, we must take a look in the past. Equestria, a land previously consisting of peace and harmony, thriving with the new arrival of the Princess of Friendship. More and more ponies felt safe and secure with the Elements of Harmony on their side, fighting the evil off. Or so they hoped. You see, as an outsider looking in, all anypony could possibly see were the problems these mares faced, and their solutions to said problems. What nopony realized was, the majority of the time, they had truly been corrupting the land.
And so it began, a war between the Elements and Celestia. Luna and Cadance eventually fought alongside Twilight Sparkle, knowing there was no hope fighting Celestia's cause.
Of course, the pacing of this explanation is probably much too quick, at least for someone who spends their free time reading My Little Pony: Friendship is Magic fanfiction. The details of said occurance are actually quite trivial. Some believe Celestia was the truly corrupt one, and the Elements had merely been attempting to fix the broken land and restore it to its former glory. Not much more can be said about the matter, other than Twilight losing the war.
Yes, Twilight had lost. Her friends were slaughtered, her family were enslaved. Celestia approached her castle, cast her spell, and poof. The castle was gone. Twilight, to prevent her own death, used her magic to transform herself into the best camoflague: a potato.
Either nopony noticed, or nopony cared. What harm could a potato do?
In the end, however, Celestia had also lost. Almost all major cities were destroyed in the event, and the majority of ponies would no longer listen to her. Only hours later was she discovered by Luna. The two fought it out, and neither sister had survived.
With three sisters dead and one a starch, Equestria fell. But to a potato, an immortal potato, the world was still just as alive.
