The outlander pony, Bow-Ayn, along with her 'stallion' friend Breach, work to find acceptance in Equestria from the shackles of their homelands.
Bow seeks to find a home among those who fear the 'true' dapple-flanks, outlander ponies from a realm across the sea who live murderous lives under a tyrannical rule.
Breach, while not a real pony, uses the guise of a unicorn to hide from his own origins. He's not just an outlander, but an outworlder. Hailing from the pits of Tartarus, he is a Daemon, but he finds no place in the abyss, and manages to break into our plane, of existance, finding solace in nature, despite his origins.
Bow and Breach formed a fast bond and eventually find them selves in Equestria tailed by assassins, which is where our story begins.

(With references to other stories by other authors, Cloudy Skies TwiDasih Fic and CoolStoryBronny's Scootaloo(spoiler alert, I don't know how it ends but what I've read made a good set-up) story, because I like them, also will have references to Where the Earth meets Sky fic, also by Cloudy Skies.
Stay pony my friends. I've added 'sex' to the rating, while it doesn't get into the topic, it very clearly explains that it does occure without directly saying it. It's not dirty or anything =P. and it only happens once so far(with doubts to having it 'occur' again).