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I can go into a little detail, I've researched a little online but feel my world is a slightly deviant case.
I'm trying to create life on a very hot, volcanic planet: one orbiting a gas giant, and with a large moon, so there is a lot of volcanic activity. I imagine a world, simply, with seas of magma, and small islands of rock.
I have creatures who use fire as there energy source, effectively finding fuel in the environment to set fire to, and power internal energy systems.
I'm having trouble figuring out how they would move (they be made of rock/or metal). I considered a system with legs made out of metal filings, using magnetism to control their movement, but seems like it would be very energy effiecent.
Edit: So, I'm creating this in an (alternate) world where life is an inevitablity, so it finds a way. I'm looking for a way that some rock/metal based 'creature', using fire as a fuel source, would be able to evolve movement. Wheels was simply an idea, apologies for confusion in question.