Cinder hound
Cinder hound is fire that has been given a hound's hunger. A Pyre summoning, Summon cinder hound, calls it out of the Welter, and Pyre holds its shape. It runs in low, bites, and then breathes fire over what it has bitten. Fire cannot hurt it, and cold hurts it badly. Soldiers who hear it coming often break before it arrives.
Mana sustains it, and its card sets a keep in geld as well. Withdraw the mana and it falls to embers. Its lord may do so at any time.
Some who see it for the first time take it for one of Deopa's creatures, the shapes that belong to the Deep. Pyre cultivators say no. It was never down there, they say. It is fire that was given a hound's hunger, and when its lord lets it go, it goes back into the Welter, not down into Deopa.