Eons ago, a great evil arose to destroy Equestria. The Alicorns had to join together, and sacrifice themselves to seal away this evil.
This act was lost in time. Only vague memories rest in the two survivors, Luna and Celestia.
Now, this evil has found a way out. It is up to three who had laid in secret.
One with no memory. one having been a magicked state since the sealing. One had been corrupted by the very thing he seeked to destroy.
Can they protect Equestria, or will everypony die due to there failure?

I will add tags as needed.