Even at the apex of her reign, Princess Sunset Shimmer spent every morning looking into one mirror and trying to patch it back together. She let her subjects believe that she was vain, for it kept her from revealing the danger of her work, and the other Princesses’ displeasure at it. She’d contained the danger of it as best she could, but she couldn’t let it disappear.
It wasn’t just Twilight Sparkle on the other side, maybe trapped in the human world and going stir-crazy. Sunset knew that Celestia’s second student would’ve been used to waiting thirty moons for a chance to return to Equestria, and although the world she called home might have been completely ravished by now, she was a tough cookie.
It was when she turned off the portal for maintenance, to set up some extra magical barriers and call in Discord for counsel and supervision, and he’d told her that the portal didn’t move to one place any more. It wasn’t the waypath to one Twilight Sparkle, it led to all of her, each one in turn through the same winding circuits of oblivion.
There were other Twilights in trouble, other worlds this portal could rescue her from, and if there was a way through it than entire nations could be saved. What a boon a thousand Twilight Sparkles would be to any kingdom, and what an evil to leave them to fate. She worked diligently, with all the awareness her alicorn form allowed, and waited patiently for the day it would unlock itself again. She had to overcome that entropy somehow, one of the few things that could still harm her no matter how powerful her magic became.
She never stopped, or gave into despair. She simply continued inscribing magical theory and prodding its nature with experiments. And all the while, her kingdom grew and shrank, and had periods of growth that outlasted those of depression, and her subjects found her a worthwhile ruler.