The click-scrape grew louder.
It was a deliberate, unhurried sound. The sound of something that had no predators. Something that owned the dark.
Arthur reacted instantly, his voice a barely audible hiss that cut through the thick silence.
"Light out."
He snuffed the glowing crystal in his palm, plunging them into absolute, terrifying blackness. The only illumination was the faint, ghostly glow of the lichen on the distant walls, not enough to see by, but enough to make the shadows dance.
"Backs to the wall. Not a sound," Arthur commanded.
He felt Borin's massive frame become a solid presence beside him, a mountain of silent readiness. On his other side, he could hear Patrin's breath hitching, a frantic, rattling sound the old engineer was desperately trying to suppress. The man's terror was a palpable thing in the dark.
The click-scrape echoed in the immense tunnel, making it impossible to judge the distance. Sometimes it sounded far away, sometimes it sounded as if it were right on top of them.
It was a hunter's sound.
Arthur focused his Sovereign's Gaze into the oppressive darkness. His skill wasn't true night vision, but it allowed him to perceive the faint outlines of intention and energy. He saw Borin's [Controlled Battle Readiness] and Patrin's pulsing, chaotic [Abject Terror].
And then, he saw a new tag emerge from the gloom. It was a cold, alien blue. [Patrolling Sentry].
A shape began to resolve itself from the deeper blackness. It was tall, taller than Borin, and unnaturally thin. It moved with a lurching, asymmetrical gait. One of its legs was a slender, multi-jointed limb that ended in a soft pad, clicking softly on the stone. The other was a long, brutal scythe of what looked like sharpened obsidian, scraping along the floor with a rhythmic grate.
The creature's body was a mockery of geology. It looked like a pillar of rock, its hide a jagged, uneven camouflage of gray and black that blended perfectly with the tunnel walls. It had no discernible head, only a cluster of glowing, deep purple fissures near its top that pulsed with a soft, internal light.
It was a sentinel. A guardian of this dead highway.
Arthur's Gaze fed him more information as it drew closer, the details appearing like footnotes in a nightmare.
[Entity: Geode Sentinel]
[Armor Class: Geo-Adaptive Plating (Extreme resistance to physical impact)]
[Identified Threats: High-Frequency Sonic Shriek, Crystalline Spore Ejection]
[VULNERABILITY: Sustained Auditory Overload, Unplated Joint at Scythe Limb Connection]
The thing was a walking fortress with specific, exploitable weaknesses. Arthur's mind, the mind of a politician who had dismantled careers by finding a single, hidden flaw, went to work.
The Sentinel paused, its glowing fissures dimming as if it were listening. It was fifty paces away. They were hidden in the deepest shadow of a rockfall. If they remained perfectly still, it might pass them by.
Patrin's terror finally betrayed them.
A small, metallic tool—a wrench or a calibrator—slipped from his trembling fingers. It hit the stone floor with a sharp clink that sounded as loud as a cathedral bell in the crushing silence.
The Sentinel froze.
Every purple fissure on its body snapped open, flaring with violent light. A head-like appendage swiveled with impossible speed, locking directly onto their position.
It knew.
"Borin," Arthur said, his voice a low, urgent command. "On my mark."
He didn't get to finish. The Sentinel reared back and emitted a shriek. It wasn't a sound one heard with their ears alone. It was a physical weapon. A wave of pure pressure slammed into them, making the air vibrate and their teeth ache. Arthur's vision blurred, a dizzying vertigo threatening to send him to his knees.
Borin roared, fighting through the sonic assault, and charged. He was a bull made of muscle and iron.
The Sentinel responded. Its rocky hide rippled, and a cloud of tiny, shimmering particles shot from its torso, like a burst of deadly glitter. The crystalline spores.
"Don't breathe it in!" Patrin shrieked, burying his face in his sleeve.
Borin, a veteran of a thousand battles, was smart enough to swerve, letting his momentum carry him past the cloud of spores. He brought his axe down on the Sentinel's flank.
The impact was deafening. But the axe, which could shatter stone, bounced off the creature's hide with a shower of sparks, leaving only a white scratch. The geo-adaptive plating was even tougher than the Gaze had suggested.
The Sentinel swiped with its scythe-limb, faster than anything that large should move. Borin threw himself back, the obsidian blade missing his chest by a hair's breadth and carving a deep, molten-edged scar into the tunnel wall.
They couldn't hurt it. And it was just getting started.
"Borin! The noise!" Arthur shouted, his own head ringing from the shriek. "Its hearing is its weapon! Use it against it!"
The big warrior's eyes widened in understanding. He wasn't just a brute; he was a smart weapon, waiting to be aimed.
He broke off his attack on the creature and sprinted to the tunnel wall. Ignoring the Sentinel that was now charging him, Borin raised his runed axe high and slammed it flat against the smooth, resonant stone.
CLANG!
The sound was immense, a deep, earth-shaking bell tone that echoed up and down the vast tunnel, multiplying, crashing in on itself.
The Sentinel faltered. It staggered, its glowing fissures flickering erratically. The sonic shriek cut off abruptly. The sustained, chaotic noise was overwhelming its senses.
"Again!" Arthur commanded.
CLANG!
Borin hammered the wall again, creating a relentless, overwhelming peal of sound. The Sentinel was completely disoriented now, lashing out blindly with its scythe, its movements jerky and uncoordinated.
"The left side!" Arthur yelled, pointing. "Where the scraping leg meets the body! The joint is unplated!"
Borin saw his opening. He timed his charge with his next swing at the wall. As the echo of the third clang shook the tunnel, he launched himself forward, not at the creature's torso, but low, aiming for the spot Arthur had identified.
The Sentinel was still reeling, blind and deafened by the noise. It was a fatal mistake.
Borin's axe, no longer aimed at the impenetrable hide, found its mark in the complex, softer joint. It sank deep into alien sinew and cartilage with a wet, sickening crunch.
The creature convulsed. The light in its fissures sputtered and died. With a final, silent shudder, the Geode Sentinel collapsed, its scythe-limb twitching once before falling still.
Silence rushed back in, heavier than before.
Borin stood over the corpse, breathing heavily. Patrin slowly peeked out from behind a rock, his face a mess of tears and relief.
Arthur approached the dead thing, the light from his crystal playing over its strange form.
"This is no beast," Patrin said, his voice trembling as he examined the exposed joint. "The articulation… the way the plating is bonded… this was made. Engineered. It is a weapon. A biological golem."
Arthur's theory was confirmed. This was Kaelan's prison. They were standing in a sealed-off laboratory of horrors.
He had no time to contemplate the implications.
As the echoes of their battle finally faded, a new sound reached them from the darkness down the tunnel.
It was not the sound of a lone patrol.
It was the sound of a dozen, of twenty, of a hundred rhythmic, scraping clicks, all stirring from their slumber, all turning their unseen attention in their direction.
They hadn't just killed a guard.
They had rung the dinner bell for the entire prison.