The forward camp on Level Three was never meant to become a town.
The earliest reports had promised as much: a few prefabricated research huts, canvas sleep quarters, and emergency supply bins dumped beside the water until the upper tiers were mapped. That was the plan, anyway. But three years came and went, and the camp stayed put. The faces rotated out, the canvas was replaced by corrugated iron, and the riverbank became cluttered with heavy generator racks and telemetry rigs.
Hayama stood by the water's edge, watching the gray silt swirl in the current. Across the crossing, the unmapped timber rose up like a solid black wall.
"Still staring down the trees?"
Hayama didn't turn around. "I'm checking the current."
"You're obsessed, Kaito." Professor Shun Aizawa, one of the permanent hands on the third tier, shoved a chipped tin mug into Hayama's palm. The coffee was scalding, black, and tasted mostly of chicory and iron. "A normal man looks at the water. You look at the dark."
"Consistency keeps people alive down here," Hayama muttered, taking a swallow.
"That's field-speak for stubborn." Aizawa gave a short, dry laugh.
Gravel crunched under heavy boots as Mina approached, tapping the face of her slate with a gloved thumb. "What's the word from the night watch?"
Aizawa's smile died. "Eastern sector went bad around midnight. Ambient miasma spiked thirty percent."
Mina frowned. "Thirty? That's not a regular drift."
"It's pooling." Aizawa pointed a blunt finger toward the ridge. "Right over the old limestone fissure."
Hayama looked up from his cup. "The staircase site."
"Could be."
"What staircase?" Daichi strolled up, rolling his shoulders under his harness.
Mina gave him a flat look. "The one you were explicitly told to leave alone."
"Right. That one." Daichi grinned, entirely unbothered.
Hayama didn't laugh. "Did the morning sweep send drones?"
"Sent two," Aizawa said. "Lost signal the second they crossed the tree line. Static, then dead circuits." He paused, rubbing at the gray stubble along his jaw. "And the patrol found fresh tracks near the bank. Something heavy. Tusks, bone plating, roughly the size of a utility quad."
Daichi's grin vanished. "A quad? That's not a native stray."
"Suddenly not so eager to go poking around?" Mina asked dryly.
"I'm considering our tactical options," Daichi retorted.
Hayama drained the rest of the bitter coffee and tossed the tin cup back to Aizawa. "We take the bank route. Gear up."
"Watch your flanks," Aizawa warned, catching the mug. "The water keeps the predators at bay, but if something's wounded or territorial, a river won't stop it."
"Understood."
Daichi turned toward the supply depot. "I'll grab Mochi's travel cage—"
"Don't you dare," Mina cut in without looking up from her screen.
"He's field-certified!"
"He's a rodent, Daichi! If he chews through my sensor wiring in hostile timber, I'm throwing him to the crawlers."
"He has logged more tunnel hours than you have, Mina."
Aizawa watched them trade barbs all the way to the lockers, shaking his head. "Are they always like this?"
"Only when they're nervous," Hayama said.
§
Twenty minutes later, the lights of the forward camp were swallowed by the black timber.
The damp earth sucked at their boots with every step. To their left, the river churned over flat stones, its steady roar the only sound in the suffocating quiet. Mina kept her eyes glued to the telemetry screen, while Daichi carried his pack, the small wire-mesh travel box tucked tight beneath his left arm.
"Miasma is ticking up," Mina murmured. "Ten percent above baseline. Tolerable, but climbing."
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Daichi looked down at the cage. Mochi was pressed flat against the mesh, his pink nose twitching toward the dark branches of the eastern ridge. "He smells something."
"He smells rot," Mina muttered.
"Animals catch pressure drops before instruments do," Hayama said from the point. "Keep your eyes off the cage and watch the brush."
Then the forest went dead.
The underground insects stopped. The canopy ceased to rustle.
*Grrrrrhh.*
A low, wet rattle echoed from the thicket ahead.
Hayama raised a clenched fist. "Halt."
A heavy bough snapped with a sharp *crack*. The undergrowth tore open, and a slate-gray shape forced its way through the brush.
It was massive. Thick, overlapping bone plates armored its neck, and two jagged horns jutted from a snout caked in mud and dried blood. Its small, milky eyes fixed instantly on the three intruders.
"That's the one," Daichi whispered, his knuckles going white against his rifle grip.
"Hold your fire until it commits," Mina warned, bringing her weapon up.
The beast dropped its head, hooves tearing through the moss.
"Scatter!"
The boar charged.
Hayama dove left as tons of muscle and bone smashed straight through the trunk where he had been standing an instant before. The wood splintered with a deafening crash.
*Crack! Crack!*
Mina fired two controlled rounds into its flank. The lead sparked against the bone plating, tearing shallow furrows into the hide. The beast bellowed, whirling around with terrifying speed.
"Keep it off her!" Hayama shouted, firing twice into the creature's exposed haunch. "Daichi, draw its flank!"
"Why me?!"
"You're closer!"
The creature pivoted, snorting a cloud of bloody foam as it lunged for Daichi's boulder. Daichi scrambled backward, firing on the move. The round caught the beast in the softer tissue beneath its jaw. It staggered, squealing in fury, giving Mina and Hayama the angle they needed.
Three simultaneous shots hammered into its skull and spine.
The beast crashed down, plowing a trench through the dirt before rolling onto its side with a shuddering groan.
Silence rushed back in.
Daichi slid down against a tree, his breath coming in ragged gasps. "That... was definitely not a normal stray."
Hayama approached the carcass with slow, deliberate steps, scanning the bone ridges with his pocket reader. "Not from Level Two. Dense skeletal structure. Heavy marrow. This came up from below."
"From Level Four?" Mina asked, lowering her rifle with shaking fingers.
"Possibly."
A faint metallic rattle broke the quiet.
Daichi froze. He looked down.
The travel carrier lay overturned in the mud, its latch bent loose from the dive. The cage was empty.
"Mochi?"
Nothing.
Daichi's face drained of color. "Mochi!"
He dropped to his knees, frantically searching the damp dirt. A set of tiny, unmistakable paw prints led straight off the trail, heading up toward a jagged outcrop of rock.
Mina pinched the bridge of her nose. "I don't believe this."
"He went up the rocks," Daichi said, scrambling to his feet. "I have to get him."
"Five minutes," Hayama said, clipping his reader back to his harness. "We don't split up."
§
The trail ended at the mouth of a dark fissure cut into the limestone ridge.
It was a narrow, jagged opening, half-buried under tangled roots. Near the base, faint chisel marks peeked through the grime—standard survey glyphs from an old expedition.
"This is the site," Hayama muttered, scraping the moss away with the edge of his boot. "The original anomaly sector."
"The staircase cave," Mina breathed.
"Mochi went inside," Daichi said, clicking his flashlight on and aiming the beam down the damp corridor.
"We retrieve the animal and pull back immediately," Hayama said. "No deviations."
They filed into the dark.
The entrance was tight, forcing them to duck under low rock ceilings, but within a dozen paces, the passage opened into an immense subterranean chamber.
Their flashlight beams caught ancient white stone walls that stretched high toward an invisible vault. Carvings covered every square foot of the rock—not mere marks, but massive, sprawling murals. Armored figures clashing with colossal horrors; lines of soldiers bearing strange, glowing polyhedrons; a vast battlefield preserved in stone.
"Historical records?" Mina whispered, her fingers adjusting the exposure on her slate's camera.
"Look here," Daichi said, sweeping his light across the central dais.
Carved into the dominant wall was a colossal, unblinking eye, surrounded by undulating ripples that looked disturbingly like smoke. Or miasma.
*Squeak.*
From behind a collapsed pillar, a small white shape scurried out, running straight for Daichi's boots.
"There you are!" Daichi dropped down, scooping the trembling mouse into his hands. "Stupid creature. You're going to get yourself killed down here."
"He has no sense of self-preservation," Mina said, though her shoulders visibly relaxed.
Hayama wasn't looking at the mouse.
The air in the chamber had turned sharp, cold, and heavy.
"Mina. The scanner."
Mina checked the slate, and her face went chalk-white. "Readings just tripled. It's off the scale—"
The stone floor shuddered.
A hairline fracture of dark light tore across the flags in the center of the hall. Then another. With a sound like grinding teeth, slabs of ancient stone began rising out of nothingness, step by step, plunging downward into an impossible abyss.
"The stairs," Daichi whispered, backing away.
"Don't move," Hayama ordered, his sidearm drawn and raised.
The descent stretched down into impenetrable black. In Daichi's arms, Mochi began to thrash violently, his claws digging through the glove, every hair on his small body standing on end.
Deep in the pit, far below the reach of their lamps, a faint crimson spark flickered.
Then, as suddenly as it had formed, the spatial anomaly fractured.
The lowest step vanished into thin air. Then the next. Like ice dissolving in boiling water, the entire stairway melted away until nothing remained but the bare, flat stones of the cavern floor.
The silence returned, heavier than before.
Then, from deep beneath the solid floor, it came.
A sound.
A high, ragged shriek.
Human.
The cry tore through the rock, long and agonized, before cutting off into a wet, sickening choke.
Mina took a trembling step back, her hands clamped over her mouth. Daichi stood paralyzed, holding the mouse against his chest.
Something heavy slammed against the underside of the stone floor. Once.
Then, nothing.
"We're leaving," Hayama said, his voice flat, cold, and perfectly steady. "Back to the camp. Move. Now."
None of them noticed the central mural as they retreated toward the mouth of the cave.
In the dying glow of their lights, the carved eye in the ancient stone caught a faint, lingering crimson sheen. For the briefest fraction of a sec
ond, the pupil seemed to dilate.
Watching.
And far below the solid rock, the sound of dragging claws began to climb.