A few hours of aimless wandering bring the lizard to the center of the room, not that he'd be aware. The giant mushroom is so much bigger than Saul; it towers over him in such a way that he's dismissive of the shadow below. It is still warm here. Warm, damp, and not entirely unpleasant for a creature that is drawn towards such places. He felt safe here and wasn't smart enough to question it.
By now Saul had gotten a handle on the legs thing, and he'd stopped trying to masticate the ferns and the dirt, given that they'd upset his stomach something awful and now there was a perpetual ache there, one he didn't know to call hunger. He was simultaneously tired and wired, which made no sense - or perhaps just overtired, given that he'd been on quite an adventure for his little legs and he was still so very, very young.
To be honest, he didn't know what to do next. Return to one of the dirt paths, see where it led him? Go back the way he'd come - to the place with the colorful lights and the brittle stone of his beginning? If he'd had any sense at all, he'd never have left Polaris.