The Battle of the Shadow Empire. Lasting only a few hours, this was the spot where the Elements of Harmony fell, giving their lives - along with the life of Celestia - to save the world. However, the Elements themselves wiped the mind of every pony in Equestria. None knew of the battle that took place.
However, when a dark-blue alicorn showed up in several towns, asking for certain ponies, some light dawns on the subject, the Elements are reborn, and the world hangs in the balance as six ponies must overcome rivalries and competitions to save Equestria and take up their roles as the new Elements of Harmony.

EDIT: Officially cancelled, I got a similar story but WAY BETTER that's going to be uploaded at a later date.