(NOTE: Undergoing a massive rewrite due to massive dissatisfaction on the author's part. Augh.)
The last thing the Mysterious Mare-Do-Well remembered was a foalnapping that had quickly spiraled out of control. Then, to her astonishment, she’d found herself in a place that seemed straight out of an old mares’ tale—a ship that could navigate the stars, sailing a river far larger than any in all Equestria.
She learned that this river, the great Eridanus, was a bridge between worlds—and that some primeval force threatened the existence of not only Eridanus, but Equestria as well.
Meanwhile in Manehattan, whispers are traveling the streets—tales of ponies disappearing into thin air, and rumors of vicious creatures, neither equine nor beast, that can walk among ponykind without suspicion.
Now, the Mare-Do-Well must wield a magic as old as Eridanus itself to destroy this ancient evil. But is her newfound power worth turning her back on a promise she made long ago?
[EDIT 12/17/12: Tagged crossover - MLP:FiM x Karas. Karas © 2005 Tatsunoko Pro.]