The Threshold of Warmth

Direct sunlight fell across Kayadu’s face with the sudden, blunt force of a dropped ballast stone.

He jerked his chin downward into his oiled mammoth collar, his eyes watering so fiercely that the rim of the living root terrace smeared into a halo of burning amber. For thirty-two years his retinas had processed only the greasy tallow gleam of the low trenches, the blue twitch of sulfur vents, and the dead pewter daylight filtering through stratospheric cloud decks. Here, five vertical leagues above the frozen floor of Oru-Obu, the sky was not a ceiling of curdled rime. It was an open dome of naked blue, baking the petrified timber under a heat so dry it tightened the skin across his cheekbones within three breaths.

Beside him, Boma-adu hauled his thick bulk over the lip of the threshold shelf and dropped flat on his elbows, groaning into the fibrous red bark.

"Cover your eyes, boy," Boma-adu muttered, rubbing his scarred knuckles over his brow. His breathing sounded like two slate slabs scraping together. "My forehead feels scalded. My eyebrows feel naked without rime."

"Keep low," Kayadu said. His voice was cracked, raw from the yellow smoke of the chimney flue. "The air is thin, but it carries sound three times farther than mist."

He pressed his belly to the warm wood, feeling the pulse of the great bough beneath his ribs. In the lower warrens, timber was either petrified to iron hardness or rotting into spongy ice-sludge. Here, the grain yielded a hair’s breadth under his fingernails, supple and humming with sap that smelled of crushed cedar needles and sweet resins.

He crawled forward to the edge of the screening lichen curtain, easing aside a cluster of bronze fronds to study the gulf.

Across a three-hundred-pace chasm of spinning stratospheric air lay the outer terraces of Udumu-Eke. They rose in cascading tiers along the trunk of the middle sphere, banked with terraced beds that pulsed with incandescent orange fire. Living ember-moss. Acres of it, breathing out heat so dense that the air above the beds shivered in visible, liquid waves. In Oru-Obu, an elder spent half a winter guarding a clump the width of a walnut shell, blowing life into sluggish embers while children lost toes in the dark. Here, the stuff grew waist-deep, so bright it painted the bellies of overhead clouds in molten copper.

"By the bone hook," Boma-adu whispered, his shoulder pressing against Kayadu’s flank. He was squinting through his walrus-hide hood, his broad jaw slack. "Look at the orange of it, Kaya. One sack of that loam, and the fourth tier stays warm through the alignment."

"Look lower," Kayadu said, his voice flat as a river pebble.

Boma-adu’s gaze tracked downward, following Kayadu’s blackened index finger.

Between their perch and the glowing terraces hung the Verge Bridge. It was a massive span of lashed ironwood spars and braided bark stays, wide enough for four heavy sledges to cross abreast, arching across the vertical emptiness between the root-spires. It was the only crossing within four leagues that had not yet been sheared apart by planetary drift.

Yet Kayadu did not look at the decking. He looked at the rigging.

His right palm burned where the tree-wasp venom had eaten through the epidermis during the chimney ascent, the raw blisters weeping clear fluid whenever he flexed his grip. His torn shoulder sinew throbbed with every pulse of blood. Pain stripped away the drunkenness of warmth and returned him to the mechanics of cordage and timber.

Kayadu slid backward into the shadow of a cedar buttress, beckoning the two junior climbers who crouched by the flue vent with their picks across their knees.

"Stay off the deck," Kayadu ordered them softly. "Unlace your packs. We do not advance until I test the grain."

Leaving his fifty-pound ballast sack with Boma-adu, Kayadu crawled along the underside of the approach ramp, worming his body through the thick curtain of hanging beard-lichen that clung to the outer abutment.

What Kayadu found beneath the first transverse beam was not joinery. It was butchery prepared in advance.

The main suspension cables looked taut and honest from above. But where they anchored into the living timber of the spur, the copper binding rings had been backed off by two hand-widths. In their place, the struts were seated on fresh cedar shear pins, carved thin in the middle like hour-glasses.

Kayadu reached out with his left hand, his blunt thumb tracing the groove of a pin. The wood was aromatic, the chips beneath it pale and unweathered. Carved recently. No more than a sun or two ago.

He leaned farther out over the bottomless white mist, tracking the diagonal counter-braces that supported the central crown of the bridge. Ten paces beneath the walking planks, hidden from anyone walking the span, hung four supplementary rawhide lines. They were not anchored to the root terrace. They ran upward through bored wooden sleeves toward a high watch-roost perched a hundred feet up the cliff face, wrapped around a trip-winch.

A deadfall.

The bridge had not been built to bear traffic. It had been rigged to hold just enough weight to lure a raiding company to the center span. The moment thirty or forty boots hit the crown, a sentry in the upper roost would pull the cedar trip-pins, the notched shear pins would snap under kinetic shear, and the entire three-hundred-pace structure would hinge downward like an unlatched cellar hatch, emptying every living soul into the ten-thousand-mile white silence below.

Kayadu touched the pouch at his hip. Inside rested a single unbaked clay vial of tree-wasp venom, sealed with green wax—their entire remaining kinetic reserve. Beside it lay the green river-slate counter-marker he had pried from Garo’s frozen ribs the previous midday, its three kill notches smooth beneath his calloused thumb.

Garo’s squad had been butchered by shear cuts in an ambush chimney. And now this. The canopy defenders had constructed an abattoir at the threshold, waiting for starving climbers to rush toward the smell of fire.

A dry scraping sound drifted down from the far side of the chasm.

Kayadu froze against the underside of the spar, blending his mammoth-hide cloak into the dark bark fissures.

Across the Verge Bridge, at the edge of the terrace where the glowing ember-moss illuminated the mist, figures moved along the palisade. They were tall hunters in shingled ironwood cuirasses, their ashwood hunting slings hanging loose at their sides. Unlike the shivering wretches of Oru-Obu, they stood easily, their faces uncovered in the mild canopy draft.

At the head of the watch-ramp stood a woman. Even at three hundred paces, her silhouette was unmistakable: broad in the shoulders, carrying a curved flint-saw slung across her back, her gaze sweeping the near abutment with the steady, forensic patience of an owl watching a vole run.

She was not looking at the sky. She was looking at the bridge decking, her posture rigid, her fingers resting lightly on the pommel of her saw.

She was waiting for them.

Kayadu backed out of the lichen shroud with agonizing slowness, placing each boot heel into the bark grooves without snapping a single dry fiber. When he reached the cedar buttress, Boma-adu was waiting with his stone cudgel braced between his knees, his eyes hungry as he stared past the timbers at the glowing orange terraces.

"Can we cross, Kaya?" Boma-adu whispered, his voice trembling with eager gravel. "The guards look scattered. If we sprint the center span, we can breach the first moss bed before they string their slings."

Kayadu took his friend by the rough hide of his collar and pulled him down into the dirt until their foreheads almost touched.

"Step on that wood," Kayadu whispered, "and you fall ten thousand miles before your scream reaches the first cloud."

He reached into his tunic and produced his flint scraper, holding it before Boma-adu’s face.

"The bridge is unpinned," Kayadu said, pointing the flint blade toward the high roost above the mist. "It is balanced on toothpicks. If we cross, they drop the world from under our feet. If we turn back, the frost takes the warrens before the moon turns."

Kayadu turned his face toward the sunlit expanse of Udumu-Eke. The radiant heat washed over his scarred skin, mocking his parched throat and his throbbing shoulder, while across the abyss, the woman with the flint-saw raised her hand to signal the watchers on the roost.