The warmth isn't unwelcome by any means, as they cross the threshold into the new space; it soothes the aches in his joints ever-so-slightly, and, at first, he isn't sure what to chalk the bubbling up to. The sounds fill the room, but the shapes aren't anything familiar with him.

The explanation of the lava vein clears up part of why that is easily. He takes an instinctive step away from the sound of the bubbling.

"Oh--- oh! Oh, I-I see," He steps closer, the jingling of his robes only just barely cutting into the ambiance of the forge. "What are the machines used for now, then? You mentioned practicality... tools, structures, or--- the bells, maybe?"