Princess Celestia always knew that Twilight Sparkle was destined for great things, but she never revealed the source of that knowledge, not even to those closest to her. When the day of Twilight's true destiny finally arrives, can Celestia fulfill an ancient promise to save Equestia's past, present, and future, even it means saying goodbye to Twilight forever? How can Celestia refuse her mother's last wish?

Art by the inimitable Harwick

To save her sister and her faithful student, Celestia herself must travel into the ancient tunnels beneath the ruined castle in the Everfree Forest. She, and the guards who accompany her, must face the dark, twisting corridors. Still, what was Luna and Twilight's purpose at the old castle? Why were they unable to return of their own accord?

And what watches Celestia from beyond the light's edge?