If it is a human AU this could be:
Playing on the Dark Side by pjhttp://spikeluver.com/SpuffyRealm/viewstory.php?sid=10189&warning=NC-17Summary: When Buffy's mother dies suddenly, she withdraws from her friends and family, and runs away from home. Venturing the streets of L.A. by herself, she is abducted by a gang when she accidentally interferes in their business. Buffy finds herself in the middle of a cruel life, where violence and rape aren't given a second thought. Can Spike save her from this life...or can she save him? A story about rape, whether redemption is even possible, and whether love can triumph from it. In this Buffy was a runaway captured by Spike and held in an underground fighting gang. Amy was caught doing something wrong and was tortured. Harmony started out as Spike's girlfriend. And Angel was the head of the opposite gang down there.
It was a fave fic of mine but it hasn't been updated -- that I know of -- since 2006. I keep hoping though... I really really liked the Spike in it. He was the perfect combination of strength, danger, and hotness. PJ if you're out there please finish this fic!!
