By the following evening, the first bitter frost of deep winter dropped upon Mount Hongwu.
A howling north wind tore through the pine needles, coating the stone railings with jagged needles of white rime. The sky turned the color of bruised slate, spitting swirling flakes of dry snow across the mountain ridges.
Inside the grand halls of Class 1 and Class 2, heavy bronze fire bowls burned day and night.
Dense, acrid clouds of charcoal smoke hung beneath the ornate ceilings, stinging the eyes of the young nobles. Students sat cross-legged on expensive silk cushions, their teeth chattering despite three layers of fox-fur robes.
“My eyes are burning,” Lu Yan complained. He wiped soot from his nostrils with a silk handkerchief. “Can the servants not get smokeless spirit-charcoal from the capital? This mountain coal is choking us!”
“The spirit-charcoal shipment was delayed by the blizzard, Senior Brother,” a pale student shivered. He rubbed his numb toes. “The stone tiles are like blocks of ice. My spiritual energy keeps freezing in my lower spirit veins every time I try to sink my Qi.”
Half the class sat with dull carbon monoxide headaches, sneezing into their stitched sleeves, their quiet focus repeatedly broken by shivering spasms.
Meanwhile, on the western ridge, Classroom 404 stood quiet against the gale.
Inside, Frank was on his knees with a line weight, a level, and a roll of heat-softened copper tubing. The newly squared pine room was clean, bright, and fully draft-free thanks to the tight window balance weights. But the surrounding heat was hovering right around thirty-four degrees Fahrenheit.
Frank touched the cedar floor with an ungloved palm.
“Heat flow rate of bare cedar over open crawlspace is unacceptable,” Frank observed. He shook his head. “Thirty-two degrees at floor level. If you sit lotus on freezing boards for two hours, blood flow to the lower hands and feet drops by sixty percent. Sciatic nerve squeezing, muscle stiffness, zero blood-flow smooth speed. We’re installing underfloor radiant hydronic heating.”
Shitou, Ling’er, and Niu Mang—all three still wearing their yellow gourd hard hats strapped beneath their chins—stood at attention with their notepads.
“Teacher,” Shitou asked respectfully, “what’s ‘hydronic radiant heating’? Is it an ancient fire-attribute array?”
“It’s plumbing, Shitou,” Frank corrected. “Hot fluid runs through looped tubing beneath the floorboards. Heat rises through natural heat rising heat, warming the floor evenly across every square inch. No open flames, no smoke, no choking charcoal fumes, and zero hot spots.”
Frank pointed to the materials lined up against the wall.
“We have two hundred feet of half-inch heat-softened copper tubing. We have a fifty-gallon iron drum of refined stone oil—much higher boiling point and specific heat capacity than plain water, zero risk of freezing or line rusting. And here is our heat exchanger.”
Frank patted a heavy, hollowed-out block of dark fiery dark rock he had chiseled into a sealed box-shaped chamber.
On one side, inlet and outlet brass squeezing fittings were threaded into the rock. On the top sat a spring-loaded brass pressure relief valve and a counterweighted copper flap.
“Rule number two of high-pressure hydronic systems,” Frank said sternly, pointing at the brass spring. “Always install a tuned pressure relief valve. If fluid expands and has nowhere to go, your classroom becomes a fragmentation grenade. Safety margins are non-negotiable.”
“Understood!” Niu Mang shouted, scribbling Calibrated Relief Valve Prevents Heavenly Explosion in his notebook.
For the next three hours, Frank directed the installation.
Beneath the cedar floor beams, Frank and Shitou routed the copper tubing in a nonstop snake-like maze, spacing each run exactly eight inches apart. Niu Mang used copper pipe straps to secure the lines, ensuring gentle radius bends to avoid fluid bubbling blast.
Ling’er poured the clear, thick, sticky stone oil through a funnel into the sealed system, carefully bleeding air bubbles from the highest bleeder valve until the loop was full and crushing pressure steadied.
Finally, Frank inspected the empty firebox beneath the dark rock heat exchanger.
“Now for the heat core,” Frank murmured, tapping his chin. “Ordinary wood burns down too quickly. Charcoal produces ash and soot. What we need is a steady, self-sustaining high-thickness heat source with zero fine dust emissions.”
Frank knelt before the dark rock chamber.
Deep within his dantian, the Micro-Star-fire Fusion Spark drifted peacefully. That tiny, ten-thousand-Degrees of star-heat strange flaw left behind by the mysterious bug tracker.
Frank opened his internal control valve.
With tiny care, Frank dialed back the output to an absurdly tiny fraction: exactly 0.001% of a single spark. A tiny trickle of pure, packed heat star-fire, thinner than a strand of spider silk, flowed down his index finger and into the sealed dark rock core.
The spark touched the dark rock chamber. Then, the dark fiery stone ignited with a deep, golden-crimson soft glow.
The stone oil inside began to circulate via natural thermosiphon rising heat. The hot oil swelled, rising through the copper pipes, while cooler oil sank back into the dark rock core. The loop purred like a sleeping tiger, silent and vibrationless.
Warmth began to radiate upward through the thick cedar planks.
Within ten minutes, the freezing chill vanished from Classroom 404.
The heat climbed steadily to a perfect, soothing seventy-two degrees. The floorboards became delightfully warm to the touch, like sunbaked river stones on a mild spring afternoon. There was no smoke, no soot, no rotten-egg stench. Only the clean, fresh fragrance of warmed pine resin and mountain cedar.
“Take off your boots,” Frank instructed, kicking off his leather work shoes. “Sit on the floor. See how the heat spreading feels on your legs.”
The three students removed their boots and placed their bare feet onto the floorboards.
Niu Mang’s jaw dropped. A wide, blissed-out grin spread across his heavy features. “It’s... It’s like stepping into a hot herbal spring! But my feet are fully dry!”
Ling’er sat down in the full lotus position on the bare wood.
The moment her thighs and calves touched the radiant cedar planks, her breath hitched.
For five painful years, her Yin-Severing frost mutation had pooled deep in her lower-back and hip joints, a permanent layer of bone-chilling frozen ground that made sitting quiet focus feel like grinding broken glass.
Now, the steady, rhythmic warmth from the floor rose into her tailbone.
It wasn’t the crude, searing heat of a charcoal fire bowl. It was the purest, most refined building heat wave she had ever met. Streaming at the exact atom-deep hum needed to unlock frozen spirit veins!
Sssssssss...
A faint wisp of cold white vapor drifted up from Ling’er’s shoulders.
The ancient frost trauma lodged deep in her bone marrow dissolved like morning mist under a noonday sun. Her Frost-Flame Qi began to circulate with total, zero-drag speed. It spun through her Governor and Conception vessels without a single trace of pain!
Tears of pure, overwhelming thanks pricked Ling’er’s eyes.
She bowed deeply over the warm floor, her voice trembling. “Teacher... To craft a radiant formation out of mortal copper and earth, warming the very bones of heaven and earth while banishing the yin-chill... Your compassion and craft are higher than the nine heavens.”
Frank took a sip of lukewarm tea from his bamboo cup. He looked at her with mild confusion.
“It’s just hydronic blasting heat, Ling’er,” Frank said. He thought back to the Roman hypocaust systems that had kept bathhouses warm two thousand years ago without an ounce of mystical zhenqi. Aloud, he grunted: “Hot underground chimney pipes and sealed channels have always done the job. Keeping your feet warm improves breath flow to the core. Stop crying on the finish. Salt water stains the lacquer.”
While Classroom 404 basked in clean, silent warmth, something extraordinary began happening outside.
Frank had tied the hydronic dark rock core into the solid mountain bedrock via the heavy eight-foot copper grounding rod. Because of that, a tiny fraction of ringing heat energy and purified earth-vein deep ring radiated outward through the underground strata.
The sub-zero frozen ground surrounding the western courtyard thawed.
Directly outside the classroom’s double-hung sash windows stood three ancient, withered peach trees. They had been dead for over four decades. Gnarled, black trunks stripped bare of bark, frozen solid in the howling November blizzard.
The smooth-flowing earth-pulse and underground warmth soaked into their deep roots. Then, the sap inside the ancient wood began to boil with vibrant, ancient life.
Crack... Crack...
Under the swirling blizzard of falling snow, emerald green buds erupted from the black bark!
Within seconds, the buds swelled, parted, and burst into thousands of amazing, deep-pink blossoms!
The fragrant, sweet perfume of spring peach blossoms washed across the snowy western ridge. Petals of delicate pink drifted down. It mixed with the white snowflakes in a dazzling, impossible vortex of spring and winter.
Down in the main academy courtyard, several senior students were shivering around a smoking charcoal fire bowl. Just then, the sweet scent caught the wind.
“What’s that smell?” one student coughed, rubbing his watery eyes. “Is someone burning peach incense?”
“Look up at the western cliff!” another youth shrieked, pointing toward the ridge.
Dozens of students and several patrolling academy deacons rushed to the stone railing, their eyes almost bulging out of their skulls.
There, perched high on the freezing western ridge in the middle of a sub-zero blizzard, stood the renovated Classroom 404.
Through the clear glass windows, the three discarded students were visible in light tunic robes, meditating comfortably on bare wooden floors with calm smiles. And surrounding their building, three legendary dead peach trees were blooming with blazing pink flowers, shedding fragrant petals into the gale!
“Peach blossoms... In the middle of a November frost blizzard?!” a deacon stammered, his teeth knocking together. “That... That’s the legendary phenomenon of ‘Spring Returning to Withered Wood’! Only a Saint-grade domain formation can overturn the four seasons!”
“Teacher Lu...” a trembling Class 1 student whispered, looking down at his soot-stained hands. “What kind of monstrous sky relic has he buried under that floor?!”
Inside Classroom 404, Frank looked through the window, saw the pink petals blowing against the glass, and frowned.
“Great,” Frank grumbled, pulling his pencil from behind his ear. “Micro-climate heat leakage into the subsoil. The heat padding under the dark rock core must be streaming two percent of its BTUs into the root zone. I’ll have to pack more stone wool around the foundation tomorrow. Or we’ll have weeds popping through the gravel before the winter solstice.”
He turned back to his three students, who were glowing with pure, unhindered training deep ring.
“Keep circulating,” Frank commanded. “Tomorrow, we start the high-smooth speed squeezing drills.”