My organism evolved to burn anything .But it is basically a biological furnace .IT works by incinerating anymatter within it .It could vent emit smoke from its vents like openings .But what could realistically this furnace made of? what compounds are mixed in this reaction that allows it to burn any organic matter and Emit smoke?
It could be a silicon based life form. All life on Earth use primarily carbon to build the compounds that make up their cells but the element silicon is very similar to carbon, being right under it in the periodic table. Most organic compounds could theoretically use silicon instead of carbon. Your creature would look very rocky or crystalline and exhale dust rather than CO2. For the furnace aspect of the creature, you could say that the creature uses this dust it exhales to form the walls of the furnace. Silicon based life comes with its own challenges which I do not know on the top of my head so you might have to do further research or you could make your creature a sort of silicon, carbon hybrid. Also for a bonus idea, you could move the smoke vents underneath the creature and give it a wide, suction cup shaped belly to essentially turn the creature into a living hovercraft, it would be energy intensive but maybe a good emergency tactic to quickly escape predators.
Current science answer? Something close to the sea pangolin that is a super-rare snail that can be found in volcanic vents. It can withstand insane amounts of pressure (roughly 240 times the pressure at sea level) and temperature (up to 400 C) by incorporating iron into its shell
To enable all the burning, your creature has to create an oxygen rich environment inside of the "chamber" it will use for burning (which can be lined up with the same material as the snail shell) and possibly keep a very high temperature inside at all times, like the furnaces used for metal and glass processing, that are always burning