The worm's hide expanded and contracted in the slow movement of its breath.

If it is indeed a game, then I have broken the rules. The intruder is supposed to approach from the opposite direction.

The Avatar sidled up carefully and examined the carapace. There were reddened warts and large white blotches, as though its entire body was an extension of diseased human skin. Thick bristles emerged from between each segment. They would twitch with every breath.

Perhaps the intruder was never meant to catch so long a glimpse. for though being a host of disease is a source and means of isolation, such a weapon has two edges. Methinks it a most unstable concoction.

Thy intention? the Guardian inquired.

To taste its blood.

He bent down and searched for a particularly jagged piece of debris. Unfortunately, the rubble had split into a rather fine gravel, and the few bigger pieces were not of a threatening size. He settled for a bulky rock with one roughly-hewn side, and so hefted it.
The worm breathed in, and he paused to follow its example. The hide expanded, and then he swung the object in a terrific arc, smashing it into an especially transparent blotch. Hchit. He immediately took several steps back to observe the reaction.
Rather than piercing the skin, it had merely sunk through a gel-like surface and caused some more bubbling to occur. White fluid seeped out from around the puncture-wound and gushed down the creature's side. A gurgling sound became audible in a moment, after allowing for the nerves to send the pain to its poorly developed brain, and then the entire display of puss and bloated skin shifted to its side.
As the creature attempted to move itself over, the thin membranous excuse for its skin strained too far under the heavy fluids inside. Cracks and tears began to appear all over its diseased surface, and a whole rainbow of vomit-like colors began to fountain out. Trapped pockets of foul-smelling gas escaped from the disturbed monster's internal chemistry and infected the air with their presence. It was literally a sack of chemicals that finally popped.
Rather than deal with the fumes, not to mention the excruciating experience of wading through a virulent bath, the Avatar retired to the ladder and back to his original chamber. For some reason it had become a much more appealing location.

So if thou art right, this is the closet someone set this. . . biological bomb-to guard, correct?

If I am right.

He approached one of the barrels and tapped the side with his foot. It sounded hollow. The other four echoed similarly.

If only I had an instrument to broach the lids.

It would not be wise to both slay the guard and steal his goods.

If there was something within, but t'were nearly void of content. A peek within is my sole desire.

Subside in thy futile practice and exit this place. Tis void of purpose. Twas an instrument of delay, in itself.

No, but a game. The key to this puzzle lies in the circumstances.

Then, pushing one of the barrels onto its side, the Avatar rolled it over to the ladder. Apparently the tunnel above had been sloping up, for the biological fluids were now dripping down onto the lower floor.

You cannot mean to-

He positioned the barrel directly beneath the makeshift waterfall. The slightly indented lid of the barrel collected the liquid into a little pool which quickly overflowed; but within moments the foul substance had burned holes through the wood and was filling the barrel from the inside. At this point he quickly moved it out of harm's way.
Unfortunately, the contents seemed only to include some scarce remains of insect larvae.

Reagents. Typical of a mage, one would suppose.

Since thou hast satisfied thy curiosity, make haste from this place! Leave now.

And leave the others unsolved? Come now, they shall come easily after the first.