"Nothing should survive in such high temperature environment, however the internal structure of this mystic beast is beyond the understanding of men. While all creature must consume food to create energy to survive, the beast feeds on perhaps the purest form of energy, heat. Similar to plants, which require sunshine and water, in a mythical world, the closest thing that is a is a combination of the sun and water, would perhaps be lava. It's internal organs, if they can even be called organs, transform the heat into energy to "power" up this unique creature. The Lava swimmer is a slow moving beast, and swims as if it has lost its soul. Where did it come from, why did it choose to exist in such lonely world where no other lifeform exist... that's a story for another time..."
Grate creature However i have to pinpoint that heat energy is the most useless form of energy, because it's the final form of energy (Motion e. --> Heat e; Light e. --> Heat e.)