With the sixty crates of fire-glass hauled safely to the surface, the deep magazine of Val-Mora was reduced to an empty, cavernous vault of weeping granite and black silt.
Tomas and Nessa remained on the drained floor of Tier Six, fifty feet beneath the marsh. While young Darrow and the wagon drivers scraped the leftover sulfur sludge from the drain channels, Nessa tapped the rear wall with her brass land-mapper’s rod.
The rod struck the massive granite cut stone blocks with a series of dull, stony clinks. Clink. Clink. Clink.
Then, at the center of the western inner wall, the pitch changed.
The brass tip struck a six-foot slab of dressed mountain stone, producing a deep, echoing hum. A hollow, hollow deep ring that hummed through the soles of their boots like the shaking of a church bell muffled in felt.
Nessa stopped instantly, pressing her sound ear horn against the joint. “Tomas. Listen to this.”
Tomas stepped across the slick silt, planting his ash staff in the muck. He pressed his palm against the cold granite. Even through the calloused leather of his glove, he could feel a faint, rhythmic movement of air behind the stone. Not the sluggish suction of bog water, but the dry, whistling draft of an enclosed sky column.
