Byzantium

Harry's been a slave for the Dursleys for as long as she can remember and is happy in her simple life - that is, until she runs into a viciously charming knight of the King's guard and her world is turned inside out. Featuring female Harry Potter, an ancient soul bond curse, black magic in the Dark Ages, nymphs, faes, goddesses, demons, and horcruxes aplenty. A dark fairy tale AU.