I'm gonna reopen this thread because this is exactly
the story I'm trying to find and I'm hoping fresh eyes will help. I've been searching both my computer and the SR search forums for hours and I'm going crazy here. This old post is the closest I've gotten.
In addition to xappletinix's
initial description above, I also remember a scene once Spike, Buffy, Angel and Drusilla are back from hell where Drusilla's hair is all burned away (by a demon/dragon?) and Buffy goes out and shaves her head in solidarity and gets them biker style clothing to match their new look. Spike is incredibly proud of Buffy for that. Also I think all four got mystical tattoos while they were in the hell dimension (though I'm not 100% positive on this last part.)