The underground cool chamber lay twelve steps beneath the forge floor, carved directly into the living solid mountain stone of the ravine.
The air here smelled of damp stone, ancient sulfur, and stale cave water. In the center of the chamber was a trough twelve feet long, two feet wide, and three feet deep, chiseled from a single block of dark limestone.
The trough was fed by a nonstop underground spring that bubbled up from a fracture in the mountain’s roots.
The water heat was exactly three degrees.
Mo Tie knelt by the edge of the limestone trough, his sleeves rolled above his scarred elbows. Beside him were three woven reed sacks of coarse grey sea salt from the southern coastal pans, along with two wooden buckets of crushed mountain oak gall and boiled pine resin.
“Normal river water won’t work for high-hard dark metal steel,” Mo Tie muttered, dumping the first sack of salt into the trough with a dull splash. “When hot iron hits fresh water, a layer of steam bubbles wraps around the metal like a woolen blanket. The steam insulates the steel, slowing down the cooling rate. In hard steel core steel, if the cooling slows down by even one second, you get soft pearlite instead of martensite. The edge will be dead.”
Pei Jing stepped forward, taking a split-pine paddle to stir the icy water.
“The salt increases heat flow rate by forty percent,” Pei Jing noted. He watched the coarse grey crystals dissolve into the clear water. “The saline solution collapses the vapor blanket instantly, forcing liquid salt water into direct contact with the metal lattice.”
Mo Tie dumped the crushed oak gall and pine resin into the churning pool.
The tannic acid from the oak gall turned the salt water a dark, tea-like amber. Meanwhile, the pine resin formed a thin, oily film over the surface.
“The oak gall scavenges dissolved oxygen from the water,” Mo Tie said, nodding with satisfaction. “Less oxygen means less rusting pitting on the polished fullers. The resin prevents the salt water from splashing into our eyes when the steam erupts.”
The smith stood up, wiping his wet hands on his leather apron.
“The bath is ready. Go fetch the beast.”
Pei Jing returned to the upper hearth shed.
The clay-coated blade blank had been resting in the long charcoal trough for three hours. The hard coal bed was glowing with a steady, uniform cherry-red radiance. Eight hundred and twenty degrees, the critical austenite shift point where the iron atoms rearranged into a face-centered cubic crystal lattice. It dissolved the carbon into solid solution.
Pei Jing approached the trough with five-foot heavy forge tongs.
He clamped the jaws of the tongs firmly onto the eight-inch tang of the blade, wrapping both hands around the long iron handles.
The tool weighed eight pounds. The glowing blade weighed twenty-four pounds. The combined thirty-two pounds of metal sat at the end of a five-foot lever arm, exerting a huge turning force on his wrists and shoulders.
Pei Jing didn’t lift with his forearms alone.
He sank into the Python Tendon-Stretching Stance.
His heels locked against the soot-dusted flat stone slabs. His Achilles tendons lengthened, storing ground reaction force. His spinal erectors, heavy by ten days of hanging weight drills, held his stance rigidly upright. That kept the glowing blade suspended in mid-air without a fraction of an inch of trembling.
He walked down the stone stairs into the underground chamber.
The glowing blade lit the damp granite walls with an eerie, blood-red soft glow. Drops of water drops hanging from the ceiling sizzled into steam as the blasting heat swept past.
Mo Tie stood at the head of the limestone trough, holding a split-bamboo torch.
“Listen to me, boy,” Mo Tie said, his voice stripped of all gruffness, sharp as a whetted chisel. “The full-body VR must be strictly upright. Tip first, spine trailing, at an angle of ninety degrees. If the blade tilts by even two degrees to the left or right, the hot side will contract faster than the cold side. The spine will warp into a sickle. You can’t bend high-hard dark metal steel once it chills. It will shatter like pottery.”
“I understand,” Pei Jing said.
His breathing slowed to eight breaths per minute.
His heart rate leveled at forty-eight beats per minute.
Through his Joint Manipulation discipline, Pei Jing performed a micro-shift of his glenohumeral and radioulnar joints. He locked his elbows at an angle of one hundred and sixty degrees. That turned his upper hands and feet into a rigid, clockwork mid-air armature.
He set the chisel tip of the Cloud-Splitter directly over the center of the dark amber salt water.
Three feet of cherry-red steel hung motionless above the water.
“Cool!” Mo Tie roared.
Pei Jing drove his arms downward in a clean, upright stroke.
KABOOM.
The reaction was not a mere hiss. It was a bone-shaking underwater blast.
The three-degree salt water met the eight-hundred-and-twenty-degree steel with violent violence. A pillar of scalding white steam erupted from the limestone trough, roaring against the vaulted granite ceiling and rolling across the chamber in dense, choking clouds of sulfur and boiled salt.
The salt water churned into a boiling froth.
Huge heat blast waves echoed up the blade. It hammered through the five-foot tongs directly into Pei Jing’s palms.
The metal inside the water was undergoing a violent core restructuring. The face-centered austenite crystals collapsed into body-centered tetragonal martensite. Then, the steel swelled by three percent in volume, groaning with high-pitched internal stress that sounded like glass cracking under deep water.
The tongs fought to twist in his hands.
Heat gradients pulled at the left flank. Steam vortices pushed against the right flank.
Pei Jing didn’t yield an inch.
His Python Stance anchored his lower body like an iron piling driven into river silt. His tendon cross-links absorbed the violent shaking, clamping his wrists in place. That forced the blade to remain absolutely straight-across to the surface of the salt water.
Ten seconds.
Twenty seconds.
Thirty seconds.
The boiling roars subsided into a rhythmic, bubbling simmer.
The water heat in the limestone trough had risen twenty degrees, steaming gently in the cold cave air.
“Draw it out,” Mo Tie whispered through the thinning vapor.
Pei Jing tightened his grip on the tongs, lifting his arms with slow, steady traction.
The blade emerged from the dark salt water.
The thick layer of white heat-proof clay, fractured by the sudden heat shock, sloughed away in brittle chunks. It fell back into the water with soft splashes.
Beneath the clay, the steel was revealed.
The blade was no longer cherry-red. It was a dark, brooding, matte-charcoal grey, streaked with rainbow-bright purples and blues along the main edge.
Mo Tie stepped forward, his breath held tight. He held the bamboo torch within three inches of the dripping metal.
The old smith closed his single eye, sighting down the spine from the tang to the chisel tip.
He rotated the blade forty-five degrees, sighting down the left flank.
Then the right flank.
“Straight,” Mo Tie breathed, his voice trembling faintly with genuine respect. “Straight as a land-mapper’s brass rule. Not a tiny fraction of an inch of warp along three feet of hard dark metal steel.”
Mo Tie reached into his leather apron and pulled out a four-inch bronze carpenter’s nail.
He tapped the broad face of the Cloud-Splitter, right above the heavy fuller.
TIIIIIIIIIIIIIIIIING.
The sound deep ring erupted from the steel.
It wasn’t the dull, muddy clunk of pig iron, nor the brittle, sharp snap of cast white iron. It was a deep, pure, crystal-clear chime, shaking with huge clockwork energy.
The tone hung in the underground cave.
Five seconds.
Ten seconds.
Fifteen seconds.
Eighteen full seconds passed before the last ringing overtone faded into the sound of the underground spring.
Mo Tie lowered the bronze nail. His chest rising and fell beneath his soot-crusted rawhide apron. He reached out with an ungloved thumb. He ran his calloused skin along the hardened edge of the chopping head.
The steel was cold, smooth as river jade, and hard enough that the dry skin of his thumb caught against the tiny crystal-clear teeth without drawing blood.
“The bone is set,” Mo Tie said, turning to look at Pei Jing. “The core is diamond. The spine is spring steel. You have forged a weapon that can cut through thirty men without chipping a tooth.”
The old smith stepped back, crossing his arms over his chest.
“The fire and the water have done their work, boy. But a cooled blade has no teeth. It has no edge. It has no soul. From this moment on, no hammer can touch it. If you want this beast to cut, you must grind it with your own hands on the stone.”
Pei Jing looked down at the dark, dripping cleaver.
In his vision, the monospace ledger lit up with a crisp, sharp-angled glow:
Pei Jing released the tongs, wrapping his bare fingers around the cool iron tang.
The weapon was cold, heavy, and silent.
“I have the stone,” Pei Jing said.
From his travel pack, he set the Black Mountain Whetstone on the oak workbench. The dished dark rock sat dark and unbending against the lantern light, ready to receive the twenty-two pounds of raw, unground hard dark metal steel.