Celestia knows of a great darkness in the world, she knows it will not stop once the gears are set in motion. During Twilight's time within the care of the solar diarch, she learns that not all monsters are fake nor are some fairy tales based of myth.

Celestia retales the the horrors of a monster that will never stop once it has been unleashed, in hopes that Twilight will know the signs before she might meet that beast.

A grim fairy tale revisited.