Firedamp is Xaxon's Methanosian (a species from the planet Methanos) form, just as Swampfire is Ben's Methanosian form. He appears as a humanoid creature covered in green bark. He has a few black patches between his toes, on his shoulders and sides, on his neck, and on his abdomen, forming an X-shaped patch of bark. His feet are mainly green bark with black spots separating his toes. He has black circles on his hands. He has three red spikes sticking out of each shoulder and five green ones sticking out of each of his forearms. His head is shaped like a black upside-down-raindrop with a flame pattern around it. His Protomnitrix Symbol is on the center of the X-shaped bark on his chest.