Spongy Pit Without A Pendulum

"Oh." Is all he says for a moment as he watches the two come out of the darkness and approach with their duties told. "Well, no. I can make a fire well enough, but this isn't a good place to do it. I need dry stuff to burn and this is all quite wet." He points out, nudging the mud with his foot. "I can make it even if it is wet if I can get back to the surface but...why do you need it? What does it do if I make the updraft needed to carry the spores out of here? I assume that's what the fire does anyway. What happens to the spores after they leave?