You head through the mouth single file, as the passage is narrow. It is as the thief described, a supernatural darkness and quiet that envelops you. Even the normally sunny shaft with the Continual Light spell on it is brought to a dull glow, as if fighting the darkness. After a bit you come to an open area that is on the edge of the volcano.
Looking down the lava shaft, you can see the roiling red liquid and feel its heat even though it's hundreds of feet below. Looking up you can see the blue sky with some clouds, touched in pink, above the rim sixty feet above you. You've lost a sense of exactly how long you've been down here, but it is obviously late afternoon outside.
The passage, once secret, that the Einar described is plain now to the party. It will be a tight fit again, single file only, but it slopes downward and hopefully away from the maddening maze and closer toward your goal.
Actions?