A quiet pony haunts their memories. The third one. A mix of the two sisters, Lumina, also known as Lights, was forgotten, and banished from Equestria. Celestia and Luna need her again, but they are worried about unleashing the dark side of her, one that every pony should forget. The twin princesses flee to refuge, knowing Lights power is getting stronger.
This is the day where Equestria will be changed, forever.