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?
Celestia must brave the depths of her old castle to save Twilight and Luna
It should never be forgotten that those who have been touched by Tirek are forever within his grasp.