---If you have not read "An Astronomer's Light," please go read it, as you may not understand this story otherwise---
After a royal experiment goes horribly wrong, Celestia realizes that her plan to set Equestria above all other pony nations may have just doomed them all. As a Cascade Wall decimates the western island nation of Brismania, it begins to head for Equestria, de-syncing all in its path. As Celestia sends five ponies off on a dangerous mission to stop it, she realizes she may have just doomed all of pony-kind at the worst, and started a world-war at the best.