Guest's request reminds me of a fic where the big showdown is Willow performing an evil ritual in a large warehouse, with Spike is pinned against a wall as described. I also remember some of the fighting taking place in the rafters. And maybe Faith is there, too? Also, I
think the sunlight hits Spike but he doesn't dust, and Buffy or someone wraps him in a fire blanket.
123Sonja's "bringing back some ancient evil" rang a bell for me, too--a story in which Willow, fiddling around with things she shouldn't, opens a box in the Magic Shop and releases an evil...witch(?), part of a couple. The Scoobies don't notice it when the witch takes over Willow's body. Possessed!Willow performs the ritual to release the other half of the couple.
Does this help? Am I on the wrong track? Have I mashed together two different stories? Inquiring minds want to know!
