The Pyre Grag is based on one of Holmberg's earliest illustration of a Grag.  This Cald creature is not a volcanic creature, but is Cald's representative to the "Poison" power theme that runs through this expansion's creatures.  This Grag also rewards Cald regional purity with the Grag's signature move of moving energy.  He's also playable by Cald Shadow Magi, making a Core Grag deck somewhat possible.