The air was thick with the scent of damp earth and decay.Ren adjusted his grip on his sword as the faint flicker of torchlight illuminated the narrow, jagged tunnel ahead. Lyra followed close behind, bow drawn, her gaze sharp as ever. The rest of the adventuring party — six in total — moved carefully, their steps quiet against the stone floor.
They had arrived at the goblin nest before dusk, sealing two narrow exits outside just as Ren had advised. Now, as the last bit of sunlight faded behind them, the only path left was forward — into the den itself.
The deeper they went, the more oppressive the air became. Scraps of bone and rusted metal littered the ground, and the occasional goblin screech echoed faintly from deeper tunnels.
Ren raised a hand, signaling the others to halt."Light ahead," he whispered.
Faint orange glows flickered from a cavern up ahead. The group moved closer — and what awaited them made even the veterans pause.
A gathering of low-class goblins. Dozens of them. Some gnawing on bones, others sharpening crude blades of stone and scrap iron. Their greenish skin glistened with grime, their fanged grins twisted in cruel mockery.
Kara, the spearwoman leading the front, took a slow breath. "There must be at least fifty of them… gods."
Ren's eyes narrowed. "If we rush in, they'll swarm. Lyra, take the left perch and provide cover. I'll draw their attention. The others hold formation and clean up the rest."
Lyra nodded, scaling a small ledge with effortless grace, her bow already drawn.
A heartbeat later, Ren stepped into the open. The nearest goblin hissed in alarm — then howled, raising its jagged knife. The den exploded into chaos.
"Now!" Ren shouted.
Arrows whistled through the air — three in perfect succession. Each shaft found its mark, dropping goblins before they could even raise their weapons. Kara charged next, her spear sweeping through the crowd like a storm, forcing a gap in the ranks.
Ren met the first wave head-on. His sword cut through the nearest goblin's chest, spun, and sliced into another's throat. He moved with calm precision, every motion efficient — no wasted effort, no unnecessary flourish.
A goblin lunged from behind, only to find Ren's elbow smashing into its skull before a blade silenced it. His Combat Instinct guided every movement, reacting faster than thought.
Lyra's voice echoed from above. "Right flank — incoming!"
Ren turned just as a cluster of goblins rushed from a side tunnel. He raised his hand instinctively, channeling mana. The air shimmered — Arcane Bolt flared to life and shot forward, piercing through two goblins and searing a third.
The battle raged for several minutes, the narrow cavern amplifying every clash of steel, every guttural shriek. Slowly, the horde began to crumble under the coordinated assault.
By the time silence finally fell, nearly fifty goblin corpses littered the ground, their blackish blood soaking the earth.
Everyone exhaled as one. Kara leaned on her spear, sweat beading down her forehead. "That… that was too many for a low-class den."
Lyra dropped from her ledge, landing lightly beside Ren. "And their numbers were growing," she murmured. "If we hadn't found this early, it could've turned into an outbreak."
Ren nodded grimly, scanning the tunnel's deeper end. Something tugged faintly at his senses — not danger, but curiosity. The faint residue of mana in the air was unnatural for low-class monsters.
"We should check further," he said quietly. "If there's a breeding pit or a higher-ranked goblin, we can't leave it behind."
Kara frowned but nodded. "We'll move carefully. Everyone, check your wounds and rest for two minutes. Then we clear the lower chamber."
As the others tended to their injuries, Ren crouched near one of the bodies. A thin layer of dark moss clung to the goblin's arm, still faintly glowing with residual mana. He touched it carefully, feeling the pulse.
"…This isn't natural," he murmured.
Lyra glanced over. "What do you mean?"
Ren stood, his eyes narrowing toward the faintly trembling wall ahead — where the tunnel continued deeper, vanishing into shadow. "Something's feeding them. This isn't just a nest."
Lyra followed his gaze. Even without words, she could feel it too — the subtle hum beneath the stone, the unnatural warmth of mana bleeding from below.
The rest of the group didn't notice it, but Ren did. His Mana Sensitivity pulsed faintly, warning him.
Something waited below.
And it wasn't just goblins.
Ren sheathed his sword slowly, his gaze never leaving the darkness ahead. "We move soon," he said quietly. "Whatever's down there… we end it before it spreads."
The flickering torchlight cast long shadows behind him, and in that moment, the cave seemed to exhale — a faint, rumbling sound echoing from the depths.
The faint rumbling in the tunnels grew louder as Ren and the others began to move again, their torches casting wavering shadows along the damp stone walls. The air felt heavier here — thick with the scent of iron, smoke, and mana that shouldn't have existed in a place like this.
Ren led the way, Lyra following close behind while Kara and the other adventurers watched their flanks. Every step deeper brought a growing unease, the faint hum of something unnatural seeping into their bones.
"Stay alert," Kara whispered. "Something's wrong with this place."
Ren didn't respond — he could feel it too. His Mana Sensitivity (Master) flared softly, reading faint currents of corrupted mana. It twisted unnaturally, almost like something had been fed into the soil.
As they turned a corner, the tunnel widened into a cavernous lower chamber. There, beneath a jagged arch of stone, stood the cause of the disturbance.
A massive goblinoid figure — easily twice the size of the ones they'd slain earlier — loomed before them. Its skin was a deeper, bruised green, its muscles corded and twitching. Eyes burned faintly crimson in the darkness, and steam rose from its body with every ragged breath.
Kara's eyes widened. "A… Hobgoblin?! That's impossible. These are D-rank threats — not something that should exist here!"
Even the veterans among them took a step back. Low-class goblins couldn't evolve naturally without years of survival and bloodshed — and yet this one looked newly transformed, unstable, almost… forced.
Ren's gaze narrowed. A faint blue shimmer appeared in his vision as the system brother's window flickered alive before him.
[Quest Generated — Forced Evolution Detected]A goblin within this den has undergone unnatural forced evolution to the next stage.Classification: Hobgoblin (Level 12)Threat Assessment: Capable of rendering an entire region uninhabitable within days.
Objective: Slay the Hobgoblin before the mutation spreads.Reward: Determined upon completion.(— Cause of forced evolution unknown —)
Ren's pulse quickened. Forced evolution…? How is that even possible?
The Hobgoblin let out a guttural roar that shook dust from the ceiling. Its crimson eyes locked on them — intelligence flickering faintly behind the madness. Then it charged.
"Positions!" Kara shouted, raising her spear.
The adventurers scattered. Lyra leapt back, arrows already flying — three bolts streaking through the air and embedding into the beast's shoulder. It barely flinched, its massive arm swinging wide and shattering a stone pillar beside it.
Ren moved forward, slipping through its blind spot. His body responded instinctively, the Combat Instinct (Expert) kicking in. He slashed upward, striking the creature's flank, but it merely staggered, roaring in fury.
"Ren!" Lyra called out, "It's regenerating!"
Indeed, the wound was already closing — skin knitting together unnaturally fast. Something was driving its body far beyond natural limits.
Ren's mind raced. "We need to exhaust it — strike vital points and avoid direct clashes!"
The group obeyed. Kara lunged with her spear, catching the beast in the ribs while Lyra rained arrows from above. Ren darted in and out of reach, every blow measured, every dodge refined.
Minutes felt like hours as they fought in that confined space. Finally, as the Hobgoblin raised its arm for one last devastating swing, Ren gathered his mana and thrust his hand forward.
Arcane Bolt!
The glowing projectile burst through the creature's chest, followed by Kara's spear impaling its heart. It let out a final, guttural roar — then fell, the cavern trembling as its body hit the ground.
For a long moment, silence filled the chamber.
Ren exhaled, lowering his blade. The oppressive pressure lifted. The others began to relax — some even laughing nervously in relief.
But Ren didn't join them. He stared at the Hobgoblin's corpse — and what lay beneath it.
A faint, pulsing crystal half-buried in the dirt. Dark veins of energy spiraled from it, still faintly glowing, slowly fading now that its host was dead.
Lyra knelt beside him. "What is that?"
Ren shook his head. "Something that doesn't belong here."
Kara approached, eyes narrowing. "Looks like a corrupted mana crystal. But this… this level of concentration shouldn't exist in this forest."
Ren crouched, carefully wrapping the crystal in a piece of thick cloth. "We'll take it to the guild. They'll want to see this."
As the others prepared to leave, Lyra's sharp gaze caught a faint glimmer in the corner of the room — half-buried under a pile of rubble.
"Ren… look at that."
They cleared the stones, revealing a small wooden chest, bound in worn iron. Inside, nestled among dust and cobwebs, lay several old coins, a silver ring engraved with leaf patterns, and a tiny vial of liquid that shimmered between green and blue.
Kara whistled. "Looks like this goblin den had more than just monsters."
Ren's eyes lingered on the vial. The mana within it felt… pure. A stark contrast to the corruption that had tainted everything else here.
He pocketed the vial carefully. "Whatever's going on, this isn't over. That Hobgoblin didn't evolve on its own."
As the group began their ascent back toward the surface, Ren looked back one last time. The crystal's fading glow pulsed faintly — like a heartbeat struggling to continue.
Something had fed the goblin power it was never meant to have.Something still out there in the forest.
And though the mission was complete…Ren could feel it deep down — this was only the beginning.