There's this.
http://spikeluver.com/SpuffyRealm/viewstory.php?sid=37283&warning=12Spirit Indestructible by Passion4Spike Rated: AO-AdultsOnly [Reviews - 359]
Summary: Season 5. Begins with 'Spiral' in the abandoned gas station, and goes *far* off-canon almost immediately.
When Dawn makes the ultimate sacrifice to save her sister, friends, and the world, Buffy's mind snaps. When Buffy's friends give up hope of her ever recovering, and become afraid that she'll turn violent and uncontrollable, they call in the Council to help. Fearing what the Council will do, Spike, forgotten and ignored by her friends, steps in. Will he be able to reach the Slayer when no one else could? Will he be able to keep her out of the hands of the Council and away from her 'helpful' friends? How much heartbreak, guilt, and failure can one girl stand before her indestructible spirit finally resigns the fight and gives up hope?
WARNINGS: Threesome B/G/G action involving Spike, Buffy, and BuffyBot. Main
Character Death. Plenty of angst.