Be warned this is not a happy Spuffy ending. It does have evil Spike. It's not a long fic.
Out of the Light by Laure Alexander
http://www.cryptoffic.com/author/k-o/laure/laure_outofthelight.htmlA challenge response set after Harsh Light of Day, what if Spike had gotten the Ring of Amara back? Who would he go after? I chose Buffy. Of the requirements I used a Playstation and Lindsey McDonald. Spike POV.
Warning: Rated NC-17, Bondage, non-consensual sex
This author does have some good dark Spuffy fic.
Link to her fics on that site.
http://www.cryptoffic.com/author/k-o/laure/laure_index.html#laure_bsThis is WIP but Updated often.
A Gem of a Soul by spuffy luvr
http://dark-solace.org/elysian/viewstory.php?sid=3442&ageconsent=okSummary: Ever wonder what would have happened if Spike hadn't lost the Gem of Amarra to Buffy? If he'd won that fight instead? Warning, this story starts out very dark. Evil vampire, after all.