The mountain was becoming too complex for manual coordination. With 965 people drawing from the same geothermal pulse, the shifting of steam-valves and the routing of Deep-Rail cars required hundreds of "Logic Decisions" every hour. A human error in the valve-room could lead to a pressure-burst in the residential tiers. Kael knew that for the population to surpass a thousand, he needed a central "intelligence" to manage the mountain's metabolism. He initiated the Relay-Brain—a Tier 13 project to build a mechanical logic engine.
The technical core of the system was the Binary Steam-Gate. Kael utilized a series of small, high-precision brass pistons that could be either "Up" (1) or "Down" (0). By connecting these pistons in complex sequences, he created "AND," "OR," and "NOT" gates—the fundamental building blocks of mechanical logic. The "input" was provided by the pressure-sensors and seismic needles throughout the mountain, and the "output" was the automatic opening or closing of distant steam-valves.
"We aren't giving the mountain a soul, Elms," Kael said, his hands oily as he adjusted a timing-cam on the primary logic-rack. "We are giving it a 'Reflex.' If the pressure in Tier 4 spikes, the Relay-Brain will know and react before a human can even read the gauge. It's the only way to synchronize a city this deep."
The grit of the construction involved the "Wiring of the Stone." Instead of copper wires, the Relay-Brain used miles of "Capillary Tubing"—narrow brass pipes filled with pressurized oil. A pulse of pressure from a sensor acted as a signal, traveling through the tubing to flip a switch in the Logic Vault. The Tier 13 gallery became a forest of vibrating brass, filled with the constant, frantic click-clack of thousands of small relays processing the mountain's data.
Socially, the Relay-Brain introduced the "Technocratic Shift." A new group of Aspirants, mostly former Imperial surveyors and clockmakers, were trained as "Logic-Tenders." Their job was not to turn valves, but to maintain the "Programs"—the physical arrangements of cams and gears that dictated the mountain's responses. They were the first citizens whose labor was entirely intellectual, a sign of the barony's rising sophistication.
The system was put to the test when a high-priority alert finally shattered the peace of the command vault. It wasn't a human mistake or a mechanical failure.
The Seismic Mirror suddenly erupted in a pattern Kael had never seen: a high-frequency, rhythmic "shiver" that didn't come from the surface, but from the deep north strata, far below the level of the geothermal bore.
The Relay-Brain reacted instantly. Before Kael could reach the controls, the mechanical gates clicked into place. The "Intake Hazard" protocol was triggered; the primary ventilation fans reversed, and the heavy iron shutters on the lower hematite vein slammed shut.
"The brain saw it first," Elms whispered, staring at the white-washed wall. "Look at the frequency. It's too steady for a rock-fall."
Kael checked the "Logic-Tape"—the punched-brass strip that recorded the Relay-Brain's inputs. The signal was a Long-Range Sonic Bore. The Empire wasn't tunneling with picks anymore. They had brought a "Vibration-Drill" to the northern ridge, a massive, steam-powered hammer designed to liquify the stone and collapse the vaults from the bottom up.
The warning system hadn't failed; it had evolved. The Relay-Brain had detected the "Phase-Shift" in the bedrock minutes before the physical shockwaves could be felt by human ears.
Kael looked at the population count: 985. They were so close to the thousand-mark, a milestone that would have officially changed Ashfall from a barony to a city-state in the eyes of the old world. But the Empire was trying to ensure they never reached it.
"The logic is clear," Kael said, his voice cold. "They are trying to 'shake' us out of the mountain. If we don't find a way to damp the bedrock itself, the Iron Skeleton will turn into a cage of vibrating knives."
He began sketching the Counter-Vibration Pits—a series of deep, water-filled chambers designed to act as "Acoustic Sinks" to swallow the Empire's sonic assault.