Vestments of the Magma Wyrm.

(*updated animations*)

Demnok summons forth the Magma Wyrm from depths of the worlds molten core.

So the worm moves through the ground with a glowing pool of magma at its base. Some rocks also animate out and around the body. The golem allows for placement of fire particles (there are 11 of them). I have them set up around the base and along the back of the golem, but unfortunately the importer and test in game doesn't allow for them to be seen (default base particle at the bottom of the summon only). Valve can place them if they are set, and they are.
I know it was a crazy design. But I thought what the hell, give it a shot. :)