It was a construct built to last the ages, a great machine hoofcrafted by Celestia and her most skilled arcanists. Within its nigh-indestructible confines, the countless inhabitants of the Moon Engine system could live out their thousand-and-one-year duty, aiding Celestia in a task left unmanaged during Nightmare Moon's banishment.

And for a thousand years and eight months, all was as it should be.

...and then Trixie showed up.

Nopony anticipated quite how much damage a single pony could do. But then, nopony'd ever thought to consider somepony quite as... viral as Trixie.