Bewitch by ghostfire
One, both a royal consort and desert sorceress, ran away from a life of imprisonment in the castle. The other, bound to the temple as a priestess from birth, thought she had followed secretly. On the border of two realms, between the desert of eternal day and the dwindling twilight forests of Qua'in'thren, the priestess is discovered and the desert dweller works her hereditary magicks.
The sorceress wishes to go back to her homeland unimpeded. She sees the priestess as a threat because they are more likely to come after her, since she is essential for the worship of the forest dweller's gods. The priestess, though she had only the same intention - to escape - would be a burden. They aren't fighting. The priestess has no defense. The sorceress wishes for her to leave her, so she may go free, but as I see the magic, it has unintentionally become a spell of ensnaring, and has bound them to each other.
The sorceress was captured, enslaved, and taken from her homeland as an adolescent. The priestess is, or rather was, kept "innocent". They would use her, forcing her to perform rituals that involved the injestion of various drugs, and interpreters would take what she said in her drugged states and deliver messages to the rest of the kingdom through that. Once upon a time, the rituals were true and pure, but they were long since corrupted.
The sorceress would be punished severely just for escaping. If discovered with the priestess, her punishment would almost certainly be death. And while no one would dare harm the priestess, most of them die young anyway, as technological and medical knowledge in the kingdom are limited. The drugs frequently cause overdoses. The blood rituals can be dangerous. The fasts are sometimes taken to the point of death.
How unfortunate it is, that theirs is not the only story in this land. Would that it was so simple... Most of the people of the kingdom are good people. The land is prosperous still, though dwindling. Their royalty take male and female slaves as they have since the beginning of the kingdom, and never yet have their gods frowned on them for it. As for the priestess and sorceress, they never met before the night in which they stole away. The priestess saw the sorcess as she was escaping and managed to follow. She followed the desert-woman all the way to the outskirts of the kingdom before she was found out. No matter what perils fate lays before them now, they must face the world together, or fade to death alone.