The bottleneck was eight feet wide, ten feet high. Then he hemmed in on both sides by unworked Precambrian granite.
Lin Ke knelt on the tunnel floor. He ran his calloused palm along the seam where the stone hall narrowed into the entrance of Sub-Vault Zero. Every scratch on the floor, every fracture along the ceiling was mapped into his Sea of Mind with tiny fraction of an inch accuracy.
“Eighty-seven hertz,” Lin Ke said, tapping his iron metal pen against the stone.
The metal struck the rock with a sharp, dry tink.
A faint, shaking hum echoed down the hall. It traveled along the walls before dying away into the mountain’s roots.
“The natural ringing hum of this hall is eighty-seven hertz,” Lin Ke repeated. He looked up at Meng Shan. “If a royal strike hits this bottleneck at eighty-seven cycles per second, the ceiling will collapse on both of you. But if you tune your shield to absorb eighty-seven hertz, the hall ceases to be a trap. It becomes a waveguide.”
Meng Shan stood motionless in the center of the passage, stripped to an iron-studded leather brigandine.
His eight-hundred-jin Black Magnetite shield rested on its edge in front of him. A massive, slab-like monolith of dark, magnetic stone bound in cold-forged pig iron, its face five inches thick and pitted with the gouges of three dozen battles.
