Aecorum was once the High Prince of the Sea, who stood alongside Celestia and Luna in the battle with Discord and helped rule over Equestria. But after he used the Elements of Harmony with Celestia to banish Nightmare Moon, he left. He blamed himself for what had happened, so he erased himself from history and from the memories of everypony in Equestria, even Celestia herself! He trapped himself in a network of caves by the sea, and lived in solitude for a thousand years. But now Luna has returned, she has regained her lost power, but she can’t find her old friend. What will happen when she discovers what he did? Will she find the stallion she considered her dearest friend and convince him to return? Or will he remain alone with his guilt and shame forever?