With Celestia's health slowly declining, magically powered machines were becoming more and more difficult to maintain. The final nail in the coffin came when Luna's jealousy gets the best of her, and our dear Princess of the sun loses the companionship of her dear sister.

Eventually, all of our gears ground to a complete halt, and Equestria was forced to re-invent even our most rudimentary machines. Our standards of living were lowered, while the best and brightest were pulled from their homes to start the process of rebuilding.

Best and brightest included us, of course.

I am Twilight Sparkle, Princess of Clockwork, and we are the league of bronze.