The Cloud Chimney

Yellow vapor rose through the vertical bore like steam from a cracked kettle, carrying the stench of rotting sap and sour brine. Kayadu jammed his boot-heels into a slick knot-hole sixty yards above the corpse ledge, his mouth wrapped in grease-soaked hide to keep the acid gas from blistering his throat. He had two hours of darkness before the planetary dawn would light the canopy lip to the watch above, and every breath inside the chimney tasted like heated copper.

Below him in the dark, wood groaned under dead weight. Boma-adu was wedged twelve paces down the flue, his broad back bowed against the opposite wall while his boots scraped for purchase on greasy moss.

"Spit the rag or choke on it," Boma-adu rasped, his voice muffled by the leather tied over his chin. "This gut-rot smells like my uncle's boiled tripe. The old goat always claimed sour broth thickened the blood. At least the yellow smoke saves us the trouble of freezing our tongues off."

"Save your air," Kayadu said down the shaft. "The chimney narrows ahead. If the sulfur thickens, breathe through your wool liner."

"My liner is stiff with snot and mammoth lard," Boma-adu grunted. The fifty-pound slab of river slate at his hip knocked against petrified bark with a heavy, hollow thud. "If I suck any harder on it, I will be chewing my own teeth for breakfast."

Behind Boma-adu, the two junior climbers hung suspended on the secondary guide cord, silent as dried bats. Their packs of flint wedges and water bladders rattled whenever the wind sheared through the chimney's outer vents.

Kayadu reached up, sinking the pick of his stone axe into the seam overhead. The timber here was soft, spongy ironwood rot, saturated by centuries of sulfur condensations that wept down the flue in pale yellow beads. The axe head sank four inches into the pulp with a wet squelch, yielding almost no resistance.

He tested the hold with a cautious tug. Sap ran over his knuckles, warm and slippery as fresh grease.

"The wood is dead here," Kayadu called down. "Drive your spikes deep. Do not trust the bark ridges."

"Nothing to drive into," Boma-adu muttered from the gloom. "The shelf under my left foot feels like curdled fat."

Kayadu hauled himself up two paces, finding a firmer rib where the flue constricted to the width of a man's shoulders. Above him, a faint grey radiance seeped down the shaft—the first diffuse glimmer of the middle sphere's lower cloud deck catching the planetary dawn. The air grew thinner, warmer, and heavier with moisture. The brutal sub-zero chill of the lower abyss was receding, replaced by the suffocating damp of the upper canopy's underbelly.

A sharp crack echoed beneath him.

Decomposing timber gave way all at once with a tearing crunch.

"Kaya!"

Boma-adu's shout cut off in a choked gasp. A massive slab of punky ironwood tore loose from the shaft wall, tumbling down the vertical chimney in a shower of rotten pulp and yellow grit. The heavy sledge-man lost his footing instantly. His bulk swung out into the void of the shaft, his ironwood cudgel clattering against the rock-bark before catching in his knee loop.

The fifty-pound river-slate ballast ripped free from its timber rest, plummeting like an anchor dropped into deep water.

The single remaining ply of the main rawhide line snapped taut with a sound like a bowstring. Kayadu's split-bone anchor wedge, driven into the soft rot three paces above his head, screeched through the pulpy grain, gouging a six-inch trench through the sodden wood.

Kayadu threw his shoulder into the chimney furrow, jamming his scarred left hip against a protruding burl. The violent jerk of Boma-adu's fall nearly ripped his arms from their sockets. His boots skidded across the greasy bark, sliding two feet down the flue before his stone pick caught in a hardened resin knot.

"Hold!" Kayadu yelled through gritted teeth. His spliced harness bit savagely into his collarbone, the sinew cord groaning under the strain.

Below, Boma-adu dangled in empty air, spinning slowly in the sulfur fog. The ballast stone hung straight down between his boots, dragging fifty pounds of dead inertia toward the lower abyss. The two junior climbers were pinned against the chimney wall below him, their fingers clawing into bark seams as the guide cord vibrated under the violent shock.

The bone anchor above Kayadu gave another sickening creak. A hairline fracture split the wet grain around the horn. In three seconds, the wedge would tear out entirely, and all four of them would plunge out the bottom of the flue into ten thousand miles of white fog.

There was no time to drive another spike. His left arm was numb from the shoulder down, pinned beneath the weight of three men and fifty pounds of river slate.

Kayadu released his stone axe with his right hand, letting it dangle by its wrist loop. With two fingers, he reached into his breast pouch and pulled out an unbaked clay vial, its pine-resin seal stamped with the three dots of the lower warren alchemists.

Their second-to-last dose of tree-wasp venom.

"Boma!" Kayadu roared down the shaft. "Smash the ballast seal!"

Below in the mist, Boma-adu struck the wax capsule lashed over the ballast stone's crown with the heel of his fist. The wax burst, flooding the pre-ground ochre circle on the fifty-pound river slate with tree-wasp venom. The stone's facet hissed, smoking scarlet in the gloom.

Kayadu cracked the resin collar of his vial with his molars and spat the wax into the dark. From his belt sack, he palmed the thumb-sized slate pebble, pre-ground with dried cinnabar ochre on its flat face. Its contact circle was ground to the exact millimeter of the facet on Boma-adu's ballast stone.

He poured three drops of venom across the painted face. The chemical reaction was instant: the ochre turned a furious, smoking scarlet, matching the activated stone below and releasing an acrid reek of crushed beetles and boiled copper.

He braced his boots against the bark seam and sighted down the flue. Boma-adu was dangling fifteen feet above a broad shelf of petrified root, his boots scraping slick timber as the bone anchor above Kayadu splintered.

"Catch the rib!" Kayadu yelled.

Kayadu cocked his wrist, threw his remaining strength into his right shoulder, and whipped the linked pebble across the shaft toward the shelf wall.

The kinetic link bit instantly.

As the light pebble streaked sideways, the fifty-pound river-slate ballast at Boma-adu's hip mirrored its velocity, surging across the empty space with violent kinetic force. The ballast dragged Boma-adu's heavy bulk in an arc, sweeping him toward the petrified shelf.

The recoil slammed back through the tether. Pain detonated through Kayadu's right shoulder, tearing the spliced sinew across his collarbone as his muscles strained to anchor the momentum. His boots gouged grooves in the bark, but the resin knot held.

Across the chimney, Boma-adu slammed belly-first onto the root ledge with a hollow groan that knocked the breath from his lungs. His massive hands clamped onto the root horns like iron vices, securing his weight.

The tension on Kayadu's rawhide line dissolved into loose coils.

Kayadu slumped against the furrow, his breath ragged and raw with sulfur. His right shoulder burned as if struck by a mallet, and blistered skin peeled along his palm where the smoking venom had splashed his bare flesh. Above him, the bone anchor hung loose in its cracked furrow, held only by a sliver of bark.

Below, Boma-adu slowly rolled onto his side, spat yellow slime into the dark, and looked up through the drifting mist.

"You took your sweet time," Boma-adu rasped, his chest heaving. "That stone nearly took my ribs off on the swing."

"Next time I let the ballast take you," Kayadu said, his voice gravelly.

"You won't," Boma-adu said, testing the root horns with scarred knuckles. "Who else would carry your rocks?"

Kayadu checked his open breast pouch. Inside the hide lining lay only a single intact clay vial of tree-wasp venom. One dose left. Enough for a single strike across the canopy border, and nothing more. If they met a patrol on the bridge or were pinned on an open span, they would have to fight with flint scrapers and bare cord.

"Haul the boys up," Kayadu ordered, wiping bitter sweat from his eyes. "We are leaving this flue."

It took twenty minutes of grinding labor through the thinning yellow vapor to clear the neck of the chimney. Testing every handhold with their stone picks, the four climbers pulled themselves past the rot zone.

The sulfur reek faded, replaced by the crisp scent of damp moss and warm stratospheric wind.

Kayadu hauled his chest over the upper cleft and rolled onto a broad, level shelf of living bark.

Above them, the lightless frost of the lower world gave way to a pale expanse of amber gold, illuminated by the unseen sun of the middle sphere. A hundred paces ahead, through drifting vapor, rose the vast terraces of Udumu-Eke, glowing with the deep orange radiance of ten thousand living ember-beds.

Kayadu touched the solitary cold clay vial in his pouch and closed his fist around the stone.