These guys often drop "Pile of Doomfire Ash". Nothing listed yet, its magic, No trade, Lore. Lucy has it, but no link. This may be used (or was intended for use) in the 1.5 Epic Rogue fight. To get Culthor the Gatekeeper to spawn, by talking to the Firewatcher.
"The Firewatcher says 'To beckon the Gatekeeper we must tempt him with bits of Doomfire. I have seen fragments of it leak through the cracks of the portal. It is here, in this place. Look around! Find the four bits and bring them to me. Ha ha! Hurry, hurry _______. I cannot wait!'"
Will confirm when I get to that fight. I guess it means 4 people would have to each turn in one. If this is needed, I would reccomend the rogue turning theirs in last, just in case.
If the Gatekeeper is not up you'll need to spawn him by handing 4 different pieces of doomfire to the firewatcher (i.e. not 4 times the pile of doomfire ash as you suggested in you post).
I can't remember the names of all the pieces, but they are all dropped from different types of mobs in SolC.