It shouldn't have been a big deal. Celestia was kidnapped or knocked out or just generally made to seem powerless by whatever idiot with ill intent decided to show up on a nearly weekly basis. As the mighty and immortal Sun Princess, she could escape at any time, but she was happy to play these little games. The daring rescues and bloodless battles gave her ponies such a sense of confidence and purpose!
But this one didn't go as planned. One small, stupid mistake got her thrown to the twisted reaches of the world-prison, Tartarus. Now alone, unarmed, and barely more than mortal, Celestia wakes in a living landscape where everything has every reason to hate her.
And, far worse, she has accidentally picked up a passenger.

Sidenote: This a repost (I tried to go through official channels, I promise!) of a story I wrote long, long ago on an account I foolishly deleted. Back in those days, Tartarus hadn't shown up in an actual episode yet. It's not exactly an alternate universe situation, but it has nothing to do with the canon portrayal of the place.

Super amazing cover art by Cold In Gardez.