Instead, he gets this ancient half-collapsed tunnel full of noxious smells and ominously large cobwebs, dimly lit by the occasional luminous fungus or strangely glowing rock.

Well, looks like a new section of this crazy maze. What was it before it was half-collapsed — natural or artificial? Are the cobwebs fresh? And what's up with that rock?

The rock: strange, glowing. Sort of a turquoisey-blue.

The tunnel: this part's natural, but around the next turning he emerges from a crack in the wall of one that's clearly artificial. There are still beautifully carved stone pillars and everything.

The cobwebs: they are indeed ominously fresh in addition to ominously large. Was that an ominously loud chittering noise just now?

He'll just — head the other way, a bit. Maybe peek around the corner; he makes sure he's wearing all matte black and looking through a tiny angled-for-lack-of-reflection visor.

Maybe that's just somebody walking down the hall.

The cobwebs are much less numerous in the nicely-decorated artificial tunnel. Unfortunately, so are the glowing-rock veins and the luminous fungi.

The chittering continues, moving down the natural tunnel toward him. Yep! That's a giant spider, all right! It's waist-high and very leggy!

Okay, he'd rather stay in slightly more known territory but close quarters with a probably annoyed or hungry giant spider does not sound fun, and maybe it'll stick to its apparent territory. Out into the hall it is.

He can supply his own light; he takes a couple seconds to look around the hall for anything of more urgent concern.

Some rubble, a few scattered cobwebs, bones of mysterious origin...

Eh, par for the course at this point. And how does the giant spider feel about matters right this second?

The giant spider is apparently content to lurk in the crack in the wall and not come out into the hall to bother him.

There are two giant-spider-free directions available, and not much obviously different between the two of them. Left or right?

Stay still and listen.

Chitter. Chitter chitter.

A lizard the size of a large dog comes trotting down the hall from the left. It walks on two legs, leaning forward, with its front feet tucked against its chest and its long tail waving behind it and its long neck stretched out ahead. At first it looks like it has no head, but no, that flat red circle at the end of its neck is a mouth, lined with teeth. It points its horrible face at Thanjen and hisses.

He looks back from heading in the direction lacking the sounds of footsteps.

Ew.

(Presumably the hiss is not modulated enough to be plausibly language.)

Confidently moving on, not fleeing.

The lizard doesn't seem inclined to chase him. It picks at a pile of bones, probably looking for food, apparently not finding any.

The corridor continues onward until it comes to a T-junction. Straight ahead, more of the same; to the left, more of the same plus some piles of burning trash.

Forward, of course. Fire means recent activity, and he's trying to understand the character of this place first. And where to retreat to.

He's still moving quietly and listening for not-fire noises up ahead.