When Celestia banished Nightmare Moon, she didn't go alone, but with her loyal army. Now they're trapped in an alien environment, with tensions high and the air running out. If they don't work together, their princess will soon be alone after all.
In a steampunk reimagining of the universe, Twilight Sparkle finds perhaps the one pony as lonely as she is. It's rather unfortunate that they're on the moon.