Reincarnated with the Country System-Chapter 257: The Drowned Sanctum-Fifth Floor

A few hours later, the joint force—comprising Raihan's holy warriors, Kain's Exo Knights, and the ISSD operatives—stood united before the gate leading to the fifth floor.

The door was unlike any they had encountered before. Unlike the stone-and-metal barriers above, this one was carved from obsidian laced with pulsating silver veins. Strange symbols—not just arcane, but ancient divine glyphs—moved slowly across its surface like living things.

Raihan stepped forward.

From his inner robe, he pulled out a scroll sealed with five rings—each bearing an angelic crest, glowing with faint celestial light.

He broke them one by one, reciting in a forgotten tongue.

The language was Old Celestian, spoken only by the high priests of the Ancient Holy Empire.

His voice echoed, unnaturally clear in the stillness.

"O Flame of Origin, O Watchers of the Deep, O Blade in Silence... Grant us passage, not in pride, but purpose. "

The runes on the door flickered, realigned, and began spiraling inward until they formed a burning spiral of light.

With a groan that resonated through their bones, the gate slowly cracked open.

A hiss of cold air swept out. And beyond it, an entirely new world.

Kain was a little surprised to see this, because Bernard Empire engineers had spent hours opening these doors, even with their advanced technology.

Beyond it, the Fifth Floor revealed itself.

A drowned valley spread out before them. Towering spires pierced the surface of a dark inland sea.

Broken temples and moss-choked statues of gods long forgotten stood half-submerged.

The sky was an enclosed dome of swirling clouds, lit from beneath by a pale, bluish light that seemed to ripple like water.

Strange floating lilies drifted along the surface, glowing faintly with bioluminescent shimmer.

"By the light... " someone murmured.

Kain's brow furrowed as he looked around.

"It took our engineers hours of cutting and blasting to open the doors above. You opened this one with a scroll. "

Raihan didn't look at him.

"Because this door wasn't meant to be forced. It was sealed with celestial will. Only faith could undo it. "

Kain exhaled slowly, grounding himself. He gestured for his squad to begin deploying drones.

ISSD operatives launched sonar-pulse probes and magical scanning spheres into the misty air.

"Looks like an inland sea, " said Vera, one of the lead ISSD officers.

"We're picking up movement beneath the water. Something massive. Multiple heat sources too. Possibly mutated lifeforms. "

Raihan knelt beside the edge of the water, dipping his fingers into it.

It was cold, with a faint trace of divine energy—diluted but unmistakable.

"This is the Drowned Sanctum, " he whispered.

Kain turned to him.

"You knew this would be here? "

"Only in visions, " Raihan replied.

"But the fifth seal was always described as hidden beneath still water, guarded by the Forgotten Leviathan. "

A beat of silence passed.

"So what do we do? "

"We find the core, " Raihan said.

"But first, we must slay the guardian. "

The joint force split into five squads of ten, each led by a mix of Exo Knights, ISSD agents, and holy warriors.

Raihan and Kain remained in the central team, spearheading the expedition.

As they moved forward, the terrain shifted.

The stone paths beneath their feet were slick with moss and algae.

Half-submerged ruins marked the flooded city—temples, coliseums, and halls dedicated to lost deities.

Aquatic life moved in the waters below. But nothing natural.

Translucent fish with bones like crystal flickered past.

Floating spherical creatures with a single blinking eye followed them, vanishing when spotted.

The tension grew with every step.

"This place is so older, "

"Because it was buried and forgotten before the Dungeon grew around it, " Raihan said.

"A world the gods sealed below, hidden behind the fifth lock. "

Suddenly, a deep hum vibrated through the water.

"Movement! " came a call through the comms.

"Central basin, something huge! "

The squads converged near a ruined cathedral, its shattered dome barely rising above the water.

The central platform was sunken, creating a deep well.

Ripples churned at its center.

Kain barked,

"Positions! Set up the perimeter! "

The air thickened with power.

Then—

The Leviathan rose.

Water exploded skyward as a titanic shape burst from the depths.

A fortress-sized beast of flesh, coral, divine steel, and rotting armor.

Its body coiled like a serpent.

Its hundred eyes burned blue with ancient fury.

Bone-like wings unfurled, casting a shadow over the squad.

Where its mouth should've been, there was only a swirling void, consuming light itself.

"Target sighted! Engage! " Kain shouted.

Exo Knights took flight using jetpacks, unleashing coordinated volleys of gauss fire.

The creature roared, an otherworldly shriek that shook the cathedral ruins.

Raihan unsheathed his blade, etched with holy fire.

"O Seraphim of Flame, guide my strike! " he cried, leaping into the air.

He slammed his sword into one of the creature's eye-clusters.

The eye burst in a flare of blue ichor.

The Leviathan thrashed, smashing columns and sweeping water into a deadly tide.

"Keep moving! Don't let it target one group! " Vera shouted.

The ISSD deployed arcane mines around the ruins.

Kain swooped close, drawing fire, while Vera coordinated the mine detonation from cover.

The Leviathan retaliated.

It opened reality-rending void portals, each sucking in wind, water—and people.

One holy knight was pulled in, vanishing without a trace.

Another was torn in half by a gravitational twist.

Screams echoed across comms.

Raihan landed, rallying what forces he could.

"Shield lines up! Everyone behind me! " he roared, raising his sword.

A dome of golden light spread out, resisting the pull of the void.

The others gathered close.

Vera made the call.

"Detonate the traps. Now! "

The arcane mines detonated.

Explosions chained across the ruins, shaking the battlefield.

The Leviathan reeled, its body partially shattered by the blasts.

Kain and Raihan exchanged a glance.

"Now! Together! "

They leapt into the air—Kain wielding a gravity-saber forged from condensed neutronium, Raihan blazing with celestial fire.

They struck in unison, blades crossing through the Leviathan's pulsing heart.

The creature screamed—a sound of pure despair—and the Leviathan collapsed. Water surged, then calmed.

From its chest, Raihan retrieved a crystalline orb.

"The Core," he said quietly.

The air shimmered, and in the sky above, a rift opened. The path to the sixth floor revealed itself.