The Interior
The tunnels inside the Glass Mountain were not made of glass. That was the first thing Sable noted in the journal she carried, writing by the light of the phosphor-lantern that hung from her belt. The walls were a substance she had no name for — translucent, yes, but warm to the touch, and when she pressed her palm against the surface she could feel a vibration, low and constant, like the purring of a very large cat. The tunnel sloped downward at an angle of twelve degrees, perfectly consistent, without a single deviation in grade or direction. No natural process could produce such precision. No human engineering she knew of could either.
She mapped as she walked, unrolling her measuring cord and marking distances with chalk on the walls. The chalk marks vanished within minutes, absorbed into the surface as though the mountain were drinking them. Sable switched to scratching notations into her leather journal and measuring by pace count, the old method, the method that did not depend on the mountain's cooperation. After two hours of descent, the tunnel opened into a chamber so vast that her lantern could not find the ceiling or the far wall. She stood at the edge of it and felt the air move around her in slow, deliberate currents, as though the chamber were breathing.
In the centre of the chamber, visible only because it emitted its own faint luminescence, stood a mechanism.