I'm incredibly embarrassed because I've asked for this same fic before, but I skipped back through over a year's worth of entries and couldn't find my original request. I managed to delete a folder of bookmarks about a month ago, and this fic was in that folder. :(
As you can probably guess, this is an older fic. I don't remember the whole thing: it's AUish, taking place after
Devil's Trap. Dean escapes from the hospital with amnesia(?), dyes his hair blue, and goes after the YED. I think he traps the demon with a vacuum(?) and keeps it in a jar, and starts gaining some of the YED's qualities. Sam and John are chasing Dean around the country, and at one point Dean runs into Bobby on the road and possibly knocks him out.
Like I said, wickedly embarrassed I have to ask for this fic again. I have del.icio.us now, though - so it should be the last time! :)
FOUND!Of Bastard Saints