The success of the Chronos-Column had brought a rigid, mechanical order to Ashfall, but as the tiers deepened and the corridors grew more crowded, a biological "noise" began to compete with the clean hum of the machines. In a closed-loop system, the smallest oversight in hygiene could escalate into a catastrophe. The humid air of the Green Ring and the recycled water of the aquaculture vats were perfect breeding grounds for more than just crops and fish. Kael recognized that to sustain a population that had nearly doubled since the blockade began, the barony needed an industrial-scale defense against disease. He initiated the construction of the Bio-Foundry.
The technical core of the Bio-Foundry was the Distillation Battery. Kael utilized the excess geothermal heat to power a series of high-capacity copper stills. Unlike the small-scale alembics of a traditional apothecary, these were massive, pressurized vessels designed to distill antiseptic spirits from the fermented husks of the Green Ring's grain and the sugar-rich stalks of the bog-vines. This "Sanitary Alcohol" became the primary solvent for a new suite of industrial hygiene protocols.
"We aren't just making medicine, Mara," Kael said, watching the clear fluid drip into a lead-glass carboy. "We are making a 'Chemical Shield.' Every tool that passes between tiers, every hand that touches the intake gate, and every drop of water in the residential pipes must be treated. We are replacing the natural immune system of the surface with a mechanical one."
The grit of the Bio-Foundry lay in the cultivation of "Medicine-Fungi." In the darkness of the deepest vaults, Kael's team utilized the nutrient-rich runoff from the hydroponic terraces to grow specialized molds on beds of sterilized peat. By carefully controlling the temperature and humidity using steam-valves, they encouraged the growth of a specific blue-tinted fungus that Kael's math suggested possessed powerful antibacterial properties. This was the birth of the "Ashfall Salve," a standardized treatment for the industrial injuries and infections common in the deep-rail and foundry.
Socially, the Bio-Foundry introduced a new level of discipline to daily life. The Healers were reorganized into the "Sanitary Corps." They patrolled the tiers not just to treat the sick, but to enforce the "Wash-Cycle"—a mandatory protocol where every citizen used a standardized alcohol-based soap before entering the common dining halls or the Green Ring. For the newest Aspirants, who were used to the filth of the Imperial trenches, this was perhaps the most jarring aspect of Ashfall life: a society where cleanliness was as essential as iron.
A technical failure occurred in the "Fungi-Vault" ventilation. A secondary steam-leak caused the humidity to spike, killing a large portion of the medicinal mold and allowing a toxic black spores to take hold. The air in the lower tiers began to carry a sharp, bitter tang that made the workers' eyes water and their lungs ache.
Kael utilized the "Atmospheric Flash-Scrub." He diverted the primary high-pressure steam-line directly into the contaminated vault, raising the temperature to a level that "pressure-cooked" the mold and the toxic spores instantly. He then reversed the centrifugal fans to vent the sterilized steam through the lye-scrubbers. It was a brutal, energy-intensive solution that wiped out weeks of production, but it saved the mountain's air.
The engineering of the Bio-Foundry allowed the barony to maintain its high-density expansion without a single outbreak. As the first batches of Ashfall Salve and Sanitary Alcohol were distributed, the citizens felt a new kind of security—not against the Empire, but against the invisible threats of the dark.
The shield is holding, Elms, Kael said, inspecting a vial of the clear antiseptic. We have the bread, the time, and the medicine. But as we move toward the next thousand people, our waste-pipes are beginning to groan. The biological waste of a city this size is a resource we can't afford to just bury in a sump-hole. We need to start the Nutrient-Recycler.
Kael began the designs for Tier 11: The Digester—a massive, underground composting facility where biological waste would be broken down by anaerobic bacteria to produce methane gas for the foundry and concentrated fertilizer for the Green Ring.