Flue 4-B was a straight, basalt-hewn bore that had not seen maintenance in decades.
As Arin and Mira advanced deeper into the eight-hundred-meter run, the temperature climbed in steep, oppressive increments.
Every hundred paces, the ambient heat rose another degree, the air thickening with aerosolized kerosene, burnt lubricating oil, and the dry, suffocating grit of powdered petroleum coke.
Arin kept his compact flashlight dialed to its minimum five-lumen beam, sweeping the stone floor three paces ahead.
Above their heads, three massive, riveted iron conduits tracked along the ceiling. The steel plates groaned constantly—a rhythmic, metallic ticking as thermal expansion forced the pipes against their sliding support saddles. Thin seams of black, viscous hydrocarbon condensate dripped from corroded flange gaskets, hissing violently whenever a drop struck the hot stone flags.
"Watch the overhead joins," Arin warned quietly, his voice dry. "Condensate traps are weeping. If that oil hits your neck, it’ll take the skin with it."
Mira nodded, pulling the cowl of her gray tunic tighter around her collar. Her face was slick with sweat, the dark hair at her temples plastered flat against her skin. "How much farther?"
"Schematic marked the battery eight hundred meters out," Arin replied, keeping his stride measured and even. "We’ve covered roughly five hundred. Another four minutes at this cadence."
He checked his internal readout:
> [ENVIRONMENTAL THERMAL GRADIENT: 41°C (105°F)]
> [HUMIDITY: 45% (DRY PYROLYTIC DRAFT)]
> [PASSIVE ACTIVE: THERMAL METABOLIC STRESS TOLERANCE (+15%)]
> [METABOLIC DRAW: MODERATE HYDRATION LOSS]
> [CURRENT HP: 84/125]
> [CURRENT STAMINA: 63 → 78/105]
Walking briskly with his loaded pack and iron through a forty-one-degree ambient draft was a steady physiological tax, but his Endurance 7 upgrade held the line. His heart rate held near ninety beats per minute, and his expanded cardiovascular volume cleared the rising core heat without triggering thermal exhaustion.
Even so, the dry furnace draft pulled moisture straight from his mucous membranes.
Arin reached into his side pouch, uncapped his open water bottle, and took a small, controlled swallow. He held the cool liquid against his gums before swallowing, keeping the volume strictly measured:
> [VOLUME REMAINING: WATER BOTTLE 1 (~40%)]
> [WATER BOTTLE 2: 100% (RESERVE UNTOUCHED)]
"Drink," Arin said, glancing back at Mira. "Don't wait until your tongue swells. In dry heat, you sweat out salt before you feel thirsty."
Mira didn't argue. She unhitched her dented tin canteen, took two disciplined sips, and sealed it back at her belt.
Three hundred meters later, the low-frequency vibration that had hummed through the bedrock since Level 1 deepened into a deafening, continuous roar.
The gallery ended at a massive iron baffle-wall.
Cut into the center of the plates was an open, louvered maintenance port designed to vent exhaust gases from the refinery floor. Through the iron slats, harsh, pulsing orange and amber light flickered across the gloom, accompanied by the violent, rhythmic clanking of heavy industrial machinery and the muffled shouts of men.
Arin clicked the flashlight off and stowed it in his side pouch.
He crept to the edge of the louvered port, dropping into a low crouch behind the steel frame. Mira slid up beside him, her iron blade drawn and resting flat against her knee.
They peered through the iron slats.
The space beyond made the Retention Sump look like a staging yard.
They were looking down into Cracking Battery 3—a subterranean processing hall carved three stories deep into the basalt bedrock. The ceiling vanished fifty meters overhead into a swirling shroud of greasy, black hydrocarbon smoke, cut through by the roaring orange tongues of four open burn-off flares mounted high on the southern cliff face.
Dominating the center of the hall were six colossal, vertical cracking retorts—cylindrical iron distillation towers twelve meters high, wrapped in spiral steam jackets and reinforced with heavy forged bands. Beneath each retort, massive coke furnaces roared behind cast-iron firebox doors, venting blast-heat that made the air across the entire chamber shimmer in visible, distorting waves.
A sprawling network of elevated walkways, iron stair towers, and rail dollies connected the furnaces to elevated slag-cooling pits along the eastern wall.
And the battery was fully manned.
"Labor gang," Mira whispered, her lips barely moving against the deafening roar of the combustion blowers.
Arin’s Perception picked through the heat shimmer, mapping the personnel.
On the lower floor, twenty paces below their louvered perch, nine men in soot-blackened canvas rags were working in mechanical rhythm. Four were shoveling crushed oil shale from heavy rail carts straight into the pre-heater hoppers; three others were hauling iron ingots out of the cooling troughs with long-handled tongs; two were manually operating the high-pressure steam valves on Retort 2.
They were emaciated, their ribs stark beneath layers of black grease and blistered heat-burns. Iron collars were riveted around their necks, tethered to short guide-chains that locked into floor tracks running parallel to the furnace doors.
"Indentured survivors," Arin observed. "Chute drops who didn't pay the gate toll."
"Not just that," Mira murmured, her eyes narrowing as she pointed toward the elevated gantry running along the mid-deck of the towers. "Look at the catwalk."
Pacing slowly along the upper iron grating five meters above the labor gang was an enforcer.
He wore a heavy, flame-retardant leather forge-apron over reinforced ring-mail, his forearms protected by thick weld-splatter bracers. In his right hand, he carried a heavy, square-headed iron spud bar—a meter of solid forged steel meant for punching tap-holes in smelting furnaces, ground sharp on the chisel end.
As the man turned beneath the amber glow of a grease lantern, the interface registered his outline:
> [PLAYER: TYR]
> [LEVEL: 4]
Level 4, Arin noted, calculating the shift.
Jaxon had been Level 3—a light scout relying on bone daggers, speed, and agility. Tyr was built like a blacksmith's anvil: thick neck, heavy shoulders, and an industrial-grade pry-bar that had enough mass to cave in a human chest through a canvas pack.
At the far end of the gantry, near the base of the massive Retort 6, a second enforcer sat on an iron keg, an arbalest resting across his knees, casually turning an iron whetstone against the head of a heavy boarding pike.
> [PLAYER: KORIN]
> [LEVEL: 3]
Two combatants. One Level 4 overseer, one Level 3 sentry with ranged capability. Plus nine chained laborers who were unpredictable variables.
"Where does the exit route lead?" Arin whispered, keeping his eyes on Tyr's pacing route.
Mira pointed her finger through the lowest louver slat, aiming toward the western corner of the chamber beneath the distillation towers.
"The cracked kerosene and naphtha don't stay here," she said. "They run through gravity-feed lines into the Central Transport Tube—a rail gallery that hauls fuel drums straight down to Level 3. Behind Retort 6, there's a submerged pipe-trench where the cold condensate return lines run. It passes right beneath their sentry post."
Arin tracked the geometry:
* Their current position was an exhaust louver four meters above the main floor, situated behind a row of inactive pre-heaters.
* The pipe-trench was forty meters across the open floor, running behind the vibrating bases of the six cracking towers.
* Tyr paced a thirty-meter gantry above the retorts, turning every forty-five seconds at the central steam manifold.
* Korin sat at the northern end of the gantry with the arbalest, but his line of sight to the pipe-trench was partially occluded by the massive cylindrical bulk of Retort 5 and 6.
"The laborers," Arin said. "If we move through the ground-level shadow, will they sound an alarm?"
"Look at their necks," Mira replied, her voice cold with disgust. "The Vanguard destroys their voices when they collar them so they can't coordinate a riot over the furnace noise. They can't scream even if they see us. But if Tyr spots a shadow out of cadence, he’ll drop that spud bar from the gantry."
Arin looked at his status screen:
> [CURRENT HP: 84/125]
> [CURRENT STAMINA: 78/105]
> [UNALLOCATED ATTRIBUTE POINTS: 3]
Three points still banked.
A Level 4 enforcer in ring-mail armed with a solid iron spud bar was not an opponent Arin could tackle head-on with a bone dagger and four Strength. If combat was forced on this floor, raw physical leverage would decide the outcome in seconds.
Do not allocate blindly, Arin commanded himself. Hold the reserve until the exact mechanical failure point appears.
He reached to his pack loop, checking the grip of the Salvaged Pike Head.
The forged carbon iron was cold against his palm, its ground chisel edge sharp and ready. Durability: 27/30.
"The exhaust louver is held by four corner pins," Arin said, his fingers finding the slotted heads of the rusted iron fasteners holding the louver frame into the baffle-wall. "When Tyr reaches the far end of his walk, the furnace blowers on Retort 1 cycle their pressure stroke. The acoustic pulse will mask the sound of the pins popping."
Mira shifted her weight onto the balls of her boots, her shortsword held tight against her forearm.
"Call the drop," she whispered.
Arin watched Tyr’s heavy boots strike the iron grating forty paces away, counting down the cadence of the reciprocating blowers:
Five.
Four.
Three.
The massive cast-iron firebox beneath Retort 1 began to draw air with a rising, subterranean howl.