The vacuum-purge had left a lingering, metallic chill in the intake corridors of Outpost Alpha. The ten infiltrators were gone, their Pulse-Beacon dismantled, but the silence that followed was not one of peace. It was the silence of a held breath. On the surface, the Seismic Mirror had begun to record a new, terrifyingly rhythmic signature. It wasn't the "jitter" of a sonic bore or the march of infantry. It was a slow, heavy thud-clank—the sound of the Empire's heaviest ordnance, the "Goliath Mortars," being winched into position on the northern ridge.
Kael felt the warning at the base of his skull shift. It was no longer a sharp "ping" of infiltration; it was a low, grinding vibration of dread. The Empire was done with the surgical approach. They were preparing a Kinetic Hammer—a sustained, high-angle bombardment designed to penetrate the limestone "roof" of the mountain and collapse the upper tiers through sheer gravitational force.
"They aren't aiming for the door anymore," Kael said, his voice a hoarse rasp in the quiet of the command vault. He traced the seismic blooms on the white-washed wall. "They're aiming for the 'fault-veins.' If they hit the limestone at the right angle, the shockwaves will travel straight down the iron skeleton and shear the bolts on Tier 4."
The grit of the defense required a radical reimagining of the mountain's exterior. Kael could not thicken the limestone roof, but he could change its "Elasticity." He initiated the construction of the Shock-Buffer—a layer of "Sandwich Armor" to be deployed over the primary residential vaults. This wasn't stone or iron; it was a five-foot thick layer of recycled rubberized-sap, crushed basalt, and loose marsh-peat, held in place by a web of heavy iron netting.
"We need the mountain to 'bounce'," Kael explained to Hektor, who was supervising the frantic forging of the iron netting. "If the mortar shells hit the bare stone, the energy travels inward and shatters our arches. If they hit the buffer, the peat will compress, the sap will flex, and the energy will dissipate into the surface soil. We are turning the mountain into a 'Spring'."
The physical labor of the "Peat-Sling" was a grueling, high-risk operation. Because the Imperial mortars were already ranging the ridge, the Tier 0 crews and the newest Aspirants had to work under the cover of the "Atmospheric Diffuser's" aerosol cloud. They moved in ten-man teams, hauling sleds of wet peat and heavy rubber-mats up the hidden service-shafts. The air on the surface was freezing, the zinc-oxide mist stinging their eyes and lungs, but they worked with a desperate, silent speed. Every pound of peat laid was a second of survival for their families below.
Socially, the "Surface-Punch" threat had forced a vertical evacuation. The "Chronos-Column" now dictated the "Deep-Migration." The residential tiers in the upper limestone (Tiers 1 through 4) were designated as "Hazard Zones." Nearly a thousand people—the population now hovering at 990—were compressed into the lower hematite and basalt tiers.
The social "grit" of this density was corrosive. Families were living in the corridors of the "Green Ring," the humidity and the constant, artificial light of the arc-lamps fraying nerves. The "Sanitary Corps" struggled to maintain the "Wash-Cycle" in the crowded tunnels, and the scent of damp earth, recycled air, and unwashed bodies became the new atmospheric baseline of Ashfall.
The first mortar strike happened at midnight.
It wasn't a roar; it was a deep, bone-shaking thump that felt as if a giant had stepped on the mountain. In the command vault, the mercury pool of the Seismic Mirror erupted in a violent splash, the light-interference patterns turning into a chaotic strobe. The internal warning in Kael's head spiked to a scream.
"Direct hit on the North Ridge!" Elms shouted, clinging to the brass rail of the console. "Tier 3 is reporting 'Spall-Falls'!"
The technical failure was immediate. While the "Shock-Buffer" had absorbed the primary kinetic energy, the "Harmonic Echo" had traveled down the secondary steam-lines. A series of lead-sealed joints in the Tier 4 laundry-vats had sheared, spraying scalding water into the crowded residential corridors.
Kael didn't look at the Mirror. He felt the mountain's response through his boots. The "Iron Skeleton" was vibrating, a high-pitched, metallic "singing" that indicated the tension-rods were nearing their limit.
"The peat is holding the impact, but the stone is 'Ringing'!" Kael realized. "If we don't damp the iron skeleton, the next hit will shear the primary supports."
He utilized the "Acoustic-Fluid" injection. He ordered the "Digester" crews to pump the high-viscosity "Digestate"—the thick, liquid byproduct of the waste reactors—directly into the hollow cavities of the iron ribs. By filling the skeletal frame with a dense, non-compressible liquid, he "Deadened" the iron. The mountain stopped singing; the vibration became a dull, manageable thud.
The bombardment continued for six hours. Sixty-four heavy shells struck the North Ridge. Through the periscope, Kael watched the surface of his mountain be transformed into a jagged wasteland of craters and white zinc-dust. But the "Shock-Buffer" and the "Fluid-Damped Skeleton" held.
The grit of the aftermath was the "Damage Audit." Kael and Hektor moved through the lower tiers, their oil-lamps casting long shadows against the sweating stone walls. They found "Hairline Fractures" in the limestone arches of Tier 4—cracks that hadn't been there a day ago. The mountain had survived the hammer, but it was "tired." The stone was fatiguing.
"We can't take another night of this, Elms," Kael said, looking at a cracked rib-bolt in the Foundry. "The buffer is being chewed away, and the stone is losing its 'Grip' on the iron."
The population count remained at 990. No one had died in the bombardment, but the "Golden Finger" in Kael's head was still humming. It was a new kind of warning—a realization that the Empire wasn't just trying to collapse them. They were "Tenderizing" the stone. They were preparing for a "Surface-Breech" using a "Thermal-Drill."
"They're going to try and melt their way in," Kael whispered, touching the cold, damp stone of the ceiling. "They're going to use the craters as 'Heat-Sinks' to focus a concentrated chemical fire on our primary airlocks."
Kael looked at the "Green Ring." The dwarf-grain was drooping, the vibration of the mortars having disturbed the delicate root-systems in the hydroponic troughs. The mountain's metabolism was slowing.
"We need to stop being a target and start being a 'Void'," Kael commanded. "If they want to melt the stone, we'll give them a 'Cold-Front' they can't ignite. Start the Liquid-Nitrogen expansion. We're going to use the Bio-Foundry's cooling-units to turn the upper limestone into an 'Ice-Shield'."
The engineering of the "Ice-Shield" was a desperate gamble—a move that would permanently alter the mountain's internal climate but would create a thermal barrier that no Imperial chemical fire could penetrate.