73

Chapter 73 — The Mana River

The underground valley stretched farther than any member of the expedition could see.

At its center, the river of concentrated mana continued flowing between enormous stone cliffs, glowing with a deep blue radiance that illuminated the entire cavern. The air itself felt heavy. Every breath carried energy into the body, and even the weakest Awakeners could feel their mana responding instinctively.

But the expedition wasn't looking at the river anymore.

They were watching the monsters surrounding it.

Hundreds of creatures had gathered along the valley.

Some were beasts.

Some resembled humanoid monsters.

Others were creatures the Association had never encountered before.

Their levels varied from the high sixties to the low eighties.

Several were clearly A-rank.

And none of them were fighting.

That was what made the situation unusual.

The creatures were maintaining distance from one another, each occupying a small territory around the mana river.

The stronger monsters had the closest positions.

The weaker ones remained farther away.

It was an ordinary territorial hierarchy.

No artificial organization.

No mysterious command.

Simply competition.

Han Yerin lowered her spear slightly.

"We can't fight all of them."

"We shouldn't," Subin replied.

She glanced at him.

"You agree?"

"The monsters aren't interested in us yet."

Subin looked across the valley.

"They have something more valuable to fight over."

The mana river surged.

A wave of blue energy moved downstream.

Every monster reacted.

Heads turned.

Bodies tensed.

Some creatures moved several steps closer.

Others backed away.

The strongest monsters remained still.

They were waiting.

Subin understood why.

The river periodically released condensed mana.

The surrounding creatures were waiting for the next release.

Han Yerin looked at the technicians.

"How often does it happen?"

The technician checked the recordings.

"Approximately every eleven minutes."

"How much energy?"

"We can't calculate it accurately."

He swallowed.

"But the last surge increased the local mana concentration by nearly seven percent."

Several Awakeners exchanged uneasy looks.

Seven percent from one surge.

If that continued, the environment could become dangerously saturated.

But there was another problem.

Subin noticed several of the monsters beginning to change.

A Level 74 beast near the river suddenly began absorbing the surrounding mana.

Its body trembled.

The crystals along its back brightened.

The creature's level began climbing.

Level 74 → Level 75

Then stopped.

Another monster began absorbing mana.

Level 69 → Level 71

A third remained unchanged.

The difference wasn't simply talent.

Subin watched their bodies carefully.

Some monsters could absorb the concentrated mana efficiently.

Others couldn't.

The ones that could were naturally becoming stronger.

The dungeon's evolution wasn't random.

Resources were selecting the creatures capable of using them.

Subin's eyes sharpened.

"This place is accelerating evolution."

One of the technicians heard him.

"That's what we suspected."

"No."

Subin shook his head.

"You suspected increased monster growth."

He pointed toward the river.

"This is different."

The technician looked confused.

Subin continued.

"The dungeon isn't simply giving monsters more mana. It's creating an environment where different adaptations are being tested."

Han Yerin understood.

"Survival of the strongest."

"Not exactly."

Subin looked at the monsters.

"Survival of the most suitable."

The distinction mattered.

A physically powerful monster might not be capable of absorbing the river's mana efficiently.

A weaker creature with better mana circulation could potentially surpass it.

The ecosystem was selecting for adaptation.

And the longer this continued, the more specialized the monsters would become.

The Association leader looked toward the river.

"Then we need to stop it."

Subin turned toward her.

"Why?"

She frowned.

"Because the monsters will become stronger."

"They will."

"And eventually they'll leave the dungeon."

"Possibly."

"Then?"

Subin looked back at the valley.

"Then humanity will have stronger monsters to fight."

Han Yerin stared at him.

"You're taking this rather calmly."

Subin's expression didn't change.

"We can't stop the entire world from changing."

He looked down at Simple Edge.

"We can only become strong enough to survive it."

Han Yerin was silent for several seconds.

Then she nodded.

"Fair enough."

She turned toward the expedition.

"We'll collect as much information as possible without engaging the major monsters. Nobody approaches the mana river."

The order was passed through the group.

The technicians began setting up observation equipment.

Several scouts moved along the edges of the valley.

Subin remained near the front.

He watched the river.

There was something about its flow that interested him.

It wasn't merely mana.

The energy moved with rhythm.

Compression.

Release.

Compression.

Release.

Like a heartbeat.

But there was no living creature producing it.

The dungeon itself seemed to be circulating energy through an enormous natural system.

Subin closed his eyes.

His Sword God perception expanded.

He didn't release Sword Intent.

Instead, he observed.

Mana moved through the cliffs.

Through the crystals.

Into the river.

Then toward the enormous formation at the far end.

The formation absorbed it.

Compressed it.

And sent part of it back through the dungeon.

A continuous cycle.

Subin suddenly understood why the monsters were evolving so quickly.

They weren't simply sitting beside a mana river.

They were living inside a massive mana circulation system.

Every creature was being exposed to continuous environmental pressure.

Those capable of adapting would grow.

Those incapable would eventually disappear.

Subin opened his eyes.

"This dungeon is functioning like a training ground."

Han Yerin looked at him.

"For the monsters?"

"For everything inside it."

---

An hour passed.

The Association gathered enough data to establish several facts.

The mana river released a major surge approximately every eleven minutes.

Each surge temporarily increased the environmental mana density.

Monsters capable of absorbing the energy showed accelerated growth.

The strongest creatures occupied territories closest to the river.

The dungeon's deeper areas contained increasingly dense mana.

And the river itself appeared to be connected to a much larger underground network.

But then something unexpected happened.

A Level 68 monster began approaching the river.

It was a strange creature resembling a large feline covered in silver scales.

Several stronger monsters immediately reacted.

One Level 77 beast roared.

The silver-scaled creature stopped.

It looked at the river.

Then at the stronger monster.

Then back at the river.

It took another step.

The Level 77 beast charged.

The silver-scaled creature fled.

The larger beast pursued.

They disappeared behind a crystal formation.

The expedition heard the battle.

Roars.

Impacts.

Stone breaking.

Then silence.

The stronger monster returned alone.

Its level had increased.

Level 77 → Level 78

The technicians recorded everything.

Subin watched the monster.

It had killed another creature.

It had gained access to territory.

It had absorbed some of the released mana.

The dungeon had rewarded successful competition.

Nothing more.

Nothing less.

Then the next mana surge began.

The river brightened.

Every monster reacted.

The strongest creature opened its mouth and began absorbing the energy.

Others followed.

Subin suddenly sensed something different.

His Sword God class reacted.

[Environmental Mana Saturation: 41.2% → 45.6%]

[High-Density Mana Exposure detected.]

[Sword God Class Adaptation activated.]

Subin felt mana entering his body.

He immediately controlled the circulation.

Unlike the monsters, he didn't simply absorb everything.

His experience in the Deep Core Territory had taught him restraint.

He allowed only a small amount to enter.

Then he guided it through his body.

His mana capacity responded.

Not dramatically.

But noticeably.

The energy felt different from ordinary mana.

Cleaner.

Denser.

More compressed.

He allowed a small amount to reach his core.

His Mana stat remained unchanged.

But his understanding of mana circulation improved.

A notification appeared.

[Mana Control comprehension increased.]

Subin ignored it.

His attention was on his sword.

Simple Edge vibrated faintly.

Not enough for anyone else to notice.

Subin looked down.

The sword's synchronization remained:

99.99%.

Nothing more.

Nothing less.

But for a brief moment, the inscription became visible.

A sword is enough.

Subin smiled.

He didn't need the sword to absorb the mana.

He didn't need the sword to become stronger.

The important thing was that he could understand the relationship between himself, the sword, and the energy surrounding them.

He closed his eyes again.

The river flowed.

His breathing slowed.

His mind became still.

Then he sensed it.

A change in the mana.

Not another surge.

Something else.

The river had begun flowing faster.

Subin opened his eyes.

"Something changed."

Han Yerin immediately looked toward the river.

"What?"

"The circulation."

The technicians checked their equipment.

One of them suddenly shouted.

"Mana flow rate increasing!"

Another looked at his screen.

"Twenty percent!"

The expedition members stood up.

The monsters also reacted.

The entire valley became restless.

The river's surface rose.

Blue energy spilled over its banks.

The enormous crystal formation at the far end began glowing brighter.

Then a crack appeared.

A single crack.

Across the largest crystal.

Everyone stared.

The crack expanded.

CRACK.

The sound echoed through the valley.

Another crack appeared.

Then another.

The technicians began shouting.

"Mana concentration is reaching critical levels!"

"Everyone retreat!"

Han Yerin raised her spear.

"Back! Move back!"

The expedition began retreating.

The monsters were doing the same.

Even the strongest creatures were abandoning their territories.

The valley was becoming too unstable.

Subin remained still for a moment.

He wasn't afraid.

He was observing.

The crystal wasn't breaking because something was attacking it.

It was breaking because it had absorbed too much energy.

The dungeon's natural circulation had reached a temporary imbalance.

The result was inevitable.

The crystal shattered.

A massive wave of mana exploded through the valley.

The force knocked several Awakeners to the ground.

Subin planted Simple Edge into the stone.

The sword held.

The wave passed around him.

His coat whipped violently in the energy.

Then everything became quiet.

The enormous crystal was gone.

In its place was a deep opening in the cavern wall.

A tunnel.

A natural passage leading deeper underground.

The mana river flowed directly toward it.

Subin stared into the darkness.

Not because something was hiding there.

Because the dungeon's ecosystem had revealed another layer.

The Association technicians slowly approached.

One looked at his equipment.

"There's a passage."

Han Yerin nodded.

"Can we explore it?"

The technician shook his head.

"Not safely."

Subin looked toward the opening.

He could feel the mana flowing through it.

The density was far higher than anything they had encountered so far.

He estimated the level of the monsters beyond it.

Possibly A+.

Maybe higher.

But there was no reason to rush.

They had already achieved more than enough for a first expedition.

Han Yerin looked at him.

"Your opinion?"

Subin withdrew Simple Edge from the ground.

"We leave."

Several people looked surprised.

Han Yerin smiled.

"I thought you'd want to go deeper."

"I do."

"Then why leave?"

Subin looked at the passage.

"Because wanting to go deeper isn't the same as being ready to go deeper."

The expedition leader nodded.

"Good answer."

She turned toward the group.

"We're returning."

The decision was accepted.

The expedition began the journey back.

Subin walked at the rear.

Before leaving the valley, he looked back one final time.

The monsters were already returning to their territories.

The mana river continued flowing.

The dungeon continued evolving.

Nothing had been defeated.

Nothing had been conquered.

Yet the expedition had discovered something more valuable than another monster core.

They had discovered that Earth's dungeons were capable of natural evolution.

And if this wasn't an isolated phenomenon, every dungeon on Earth could eventually become stronger.

Subin's eyes became focused.

Humanity would have to adapt.

So would he.

A system notification appeared.

[Environmental adaptation completed.]

[Sword God Class Evolution Progress: 74% → 75%]

Subin dismissed it.

Then another notification appeared.

[Global Mana Density: Increasing.]

[Global Dungeon Evolution: Accelerating.]

[Human Awakening Rate: Increasing.]

Subin continued walking.

The age of the first awakened humans had already begun.

Now something else was beginning.

The age of evolution.