The deafening clashes of battle reverberated through the colossal cavern, each impact sending tremors through the rocky walls. The Wyvern was a force of nature, its obsidian-like scales deflecting their strongest attacks, making each strike feel insignificant. Its tail lashed out like a whip, carving deep grooves into the stone beneath them, its eyes burning with a primal fury that mirrored their own desperation.
The fight had stretched on longer than anticipated. Too long.
Vahn panted heavily, his body drenched in sweat as he formed another water barrier to shield Varek. His mana reserves were dwindling rapidly, and the dozens of elixirs he had consumed left a bitter, metallic taste in his throat. His left arm trembled from overuse, his ice-forming glove cracked and barely functioning. One of Varek's whips lay in tatters on the ground, its essence-infused strands now nothing more than useless threads.
"Varek, watch out!" he managed to shout between ragged breaths. He conjured a razor-thin water blade and flung it through the air, slicing apart an incoming spike just before it could impale his comrade.
Varek staggered back, his crimson-stained armor barely holding together. His whip was now a single strand, the once-fluid weapon feeling heavier with every movement. The gashes on his arms throbbed with pain, his body screaming at him to stop. But stopping meant death.
"Damn it," Varek muttered, gritting his teeth. His vision blurred for a second before he forced himself upright. "I wish… I had a better talent. Maybe I could actually help instead of slowing you both down."
Vahn tossed him a vial. "Shut up and drink."
With no hesitation, Varek downed the potion, feeling the rush of temporary vitality course through his veins. But even with the boost, he knew it wouldn't last much longer.
BOOM!
The Wyvern roared, shaking the very air with its cry of rage, its wings sending powerful gusts across the cavern.
Then, the tide shifted.
A sonic boom erupted from the far side of the cave as Sen's battered body shot forth like a bolt of lightning.
A low, unhinged chuckle came from the bloodied figure. His skin marred with fresh wounds, yet he stood—his grip on his axe never wavering. His wild red hair was plastered to his forehead, strands matted with his own blood. But his eyes—his eyes were different.
Glowing with a terrifying intensity, they flickered between sanity and something far more primal.
"Shit." Varek took a step back. "Not this."
Vahn cursed under his breath. "Sen… calm down. If you use it in this state—"
Lightning arced around Sen's form, sizzling against the air. His lips curled into a feral grin, one that sent a chill down both their spines.
"Calm down?" Sen's voice was a deep growl, the amusement in his tone making it far more menacing. "Come on, guys. I'm perfectly calm."
The Wyvern, sensing the shift in power, hesitated for the first time.
Sen had long activated his innate ability that made him terrifying amongst his peers. An ability that when he awakened it in his second year made even his seniors and some instructors avoid battling him. An ability that makes even those who are meant to be stronger, dread standing against Sen. It was more than an innate ability, It was--
Primal Overdrive.
It wasn't just an ability. It was madness incarnate.
Primal Overdrive wasn't a simple enhancement skill or a low-level innate ability—it was a devourer of reason and restraint. At its base level, it heightened the user's perception, battle instincts, and reaction speed, allowing them to perform at levels beyond their natural limits. But the true terror came when Sen entered Battle Trance—a state where the Overdrive effect doubled every minute.
Every fiber of his being became sharper. Every muscle, faster. Every instinct, deadlier.
His strength, speed, durability, perception, battle senses and everything that would make a human doubles as well, and if left unchecked would reach a terrifying level of strength.
But there was a price.
Primal Overdrive devoured essence at an exponential rate. The longer it remained active, the heavier the toll. At its peak, it could push the user's body to inhuman levels of endurance, allowing them to ignore injuries, to shrug off pain—but once that point was reached, there were only two outcomes:
Total essence depletion—or complete loss of control.
And right now, Sen was teetering on the edge of both.
"You idiots… don't get in my way," Sen whispered, his voice laced with static as his aura crackled.
Varek cursed. "Vahn, throw him a potion—now."
Vahn hesitated for half a second before hurling a vial through the air. Sen snatched it mid-flight, crushing the glass between his teeth as he chugged its contents, the mana elixir flooding his system.
Then he vanished.
The cavern shook as a shockwave followed his movement. The next second, Sen reappeared under the Wyvern, his axe already swinging.
The impact was catastrophic.
CRACK!
The Wyvern's head snapped back, the sheer force sending ripples through its massive frame. A loud BOOM echoed as the entire beast was lifted off the ground, its talons scraping against the cavern floor as it struggled to stabilize itself.
"Hah—" Sen exhaled, twisting midair. He spun the axe in his grip and brought it down again—this time, straight into the beast's wing joint.
A sickening tear filled the cave as part of its wing was severed.
The Wyvern screamed in agony.
"Don't slow down now!" Varek shouted, gripping his whip flinging it out to wrap around the Wyvern's foot pulling it back to lose its balance.
Sen didn't need the encouragement. He was already moving.
A surge of lightning burst from his feet, propelling him like a streak of blue death. His axe collided with the Wyvern's scales, each hit sending thunderous ripples through its body. Every strike was heavier, faster, fueled by the insatiable hunger of his Overdrive.
The Wyvern's tail lashed out in desperation—
Vahn intercepted. A massive water barrier surged into existence, dulling the impact just enough for Varek to lash out with his whip, the hooks digging into the Wyvern's flesh and anchoring it down.
"Finish it!" Vahn roared.
Sen roared back, lightning crackling around him. His pupils were narrowed to slits, his expression borderline predatory.
With a final burst of essence, he shot upward—high above the Wyvern's head.
The strength of his aura already stronger than the peak rank 2 disaster clearly bordering a rank 3. His aura filled the cave causing the disaster to freeze leaving it open of a fatal strike.
For a moment, he hovered.
Then, with a wild grin, he flipped the axe upside down, letting the weight of it guide him as he plummeted like a meteor.
CRACK!
The axe sank into the Wyvern's skull, splitting through its armored hide and lodging deep into its brain.
The monster spasmed violently—its roars turning to choked gurgles. The cavern trembled as its massive frame began to collapse.
Sen landed, his breath ragged. His arms trembled, his knees threatening to give way. His aura flickered—erratic, unstable. His body was failing, the Overdrive consuming more than he could replenish.
And yet, he still smiled.
"We… won," he whispered, his grip on his axe loosening.
Varek rushed forward, supporting his weight before he could crumple completely. "Idiot. You nearly killed yourself."
"Hah. Worth it." Sen chuckled, but it was weak. His body was shaking violently, the aftermath of Overdrive taking its toll.
Vahn let out a breath of relief. "Alright. Let's collect the—"
Then he stopped.
The air shifted.
Varek felt his stomach drop.
A sickening gurgle escaped the Wyvern's corpse.
Something was wrong.
From the gaping wound in its skull, a black, viscous substance began to seep out. It oozed like a living thing, writhing unnaturally, as though tasting the air.
Varek's mouth went dry.
"…Guys?"
Sen, barely able to stand, felt it first.
The hair on the back of his neck rose.
Something ancient stirred in the darkness.
And for the first time since they entered the dungeon—
Sen felt fear.