The fifth day began not with silence, but with sound.
Drip.
Drip.
Drip.
Water fell from cracks in the cavern ceiling, each drop echoing like a hammer against his skull. The air was damp, thick with mildew and the copper tang of old blood.
He pushed himself upright. His limbs screamed in protest, every movement a storm of agony. But this time, he did not call on the system to strip away another memory.
Instead, he whispered, "Channel pain."
And the system obeyed.
[Prototype Function: Efficiency Reinforcement (Unstable).]
[Fuel: Host's physical pain.]
[Conversion rate: 1% efficiency gain per sustained threshold.]
At once, his body ignited with torment. Each throb of his broken rib, each lash of strained tendon, became fuel. His blade flickered with blackfire brighter than ever before.
But the cost was immediate.
The pain didn't stay in his body. It bled into his mind.
When the first beast appeared, a wolf of stone and shadow, the strike came fast, jaws aimed at his throat.
He met it head-on, roaring, blackfire blade severing its skull in a spray of molten rock.
But in the echoes of that strike, he heard something.
"Weakling."
The word reverberated inside his skull. He froze. The voice was familiar, sharp, cold, precise.
The captain.
"No…" he whispered, shaking his head.
"Always the dog. Always kneeling, always obeying. Did you think loyalty was strength?"
His grip faltered. The wolf's corpse turned to dust, but the words remained.
He staggered forward. Another beast leapt, claws raking his chest. He cut it down, fire consuming its body.
This time, the voice was softer. Feminine. Warm.
"You swore you'd come back, remember? You promised me you'd return."
His chest seized. His blade nearly fell. That voice, he couldn't remember the face anymore, only the outline of a smile. Was it a friend? A sister? A lover?
The system did not respond.
The voices multiplied. Each sacrifice, each lost memory, each fragment torn away by the system, they were coming back, not as comfort, but as phantoms.
Above, in the throne hall, the Demon Lord leaned forward slightly.
"His flame flickers strangely," he murmured. His silver eyes narrowed, watching the disciple stagger through the cavern. "See how it bends? How it twists back upon itself?"
The daughter frowned. "He looks… haunted."
"Not haunted," the Demon Lord corrected softly. "Hollowed. The emptiness draws echoes."
He tilted his head, as though listening to a song only he could hear. "Every hollow vessel makes a sound when struck. The question is… will he become a flute, or a war drum?"
The daughter shivered. She did not ask what he meant.
Back in the cavern, the disciple pressed onward. Each step was agony, each strike a scream. The pain burned his flesh and shredded his sanity.
The whispers grew.
"Coward."
"Traitor."
"Brother, please don't, "
"You failed us all."
He swung wildly, slashing beasts and phantoms alike. His blade's fire howled, devouring shadow and stone alike.
His laughter came next, sharp and cracked.
"Shut up! Shut up, all of you!"
But the voices didn't stop. They twisted, merged, became a chorus.
The system chimed faintly in the storm of sound:
[Warning: Host stability declining.]
[Prototype Function instability: 68%.]
Hours bled together.
When the last beast fell, the cavern was littered with ash. His body shook, sweat pouring down his skin. His eyes were bloodshot, his lips cracked, his laughter gone.
But in the silence that followed, one whisper lingered.
Not mocking. Not cruel. Soft. Almost… proud.
"You're still standing."
His breath caught. He clutched at the words, desperate, but they slipped away. No face. No name. Only warmth.
He sank to his knees, trembling.
"…Still standing."
His blade pulsed in his grip, blackfire flickering low.
Above, the Demon Lord exhaled slowly, eyes narrowing.
"…Intriguing."
The daughter looked at him cautiously. "What did you see?"
The Demon Lord's gaze lingered on the fading image of the disciple, kneeling in the ash, whispering to ghosts.
"I saw a man who carries a graveyard in his chest," he said. "And yet, still he walks."
He leaned back in his throne, shadows curling like smoke.
"This one… will not break like the others. No, he will fracture. And in the cracks, something new will grow."
His smile was thin, unreadable. "I would like to see it."
[System Notice: Trial Complete.]
[Reward: Endurance reinforced.]
[Penalty: Mental erosion severe.]
[Prototype Function recorded.]
The disciple lay trembling, eyes closed, whispers still clinging to the edge of hearing.
But his lips moved, shaping words.
"…If pain can be fuel… then maybe… maybe I don't have to lose everything."
The fire guttered low, but it still burned.
The Furnace Path had not claimed him yet.