"Damn it..." Ning Yu gritted his teeth and persevered, a resolute glint in his eyes. "Even if it costs me my life, I will find out what exactly is attracting them!"

Ning Yu's eyes were as firm as iron. He knew that the fate of his territory hung in the balance, and finding the source attracting the monsters was his only hope. He wielded golden energy, each attack carrying the force of thunder, carving a bloody path through the monster horde.

"Boom!" A giant lizard-like monster was sent flying by his punch, its massive body crashing into a section of broken wall. But soon, more monsters surged forward, one after another, fearless and relentless.

Ning Yu felt his stamina rapidly draining away, but he didn't stop for a moment. He was like a tireless fighting machine, swinging his fists and releasing energy, carving a bloody path through the monster horde.

"Roar!" A deafening roar came from afar, and an even larger monster appeared in Ning Yu's field of vision. Its entire body was covered with thick scales, exuding a suffocating sense of oppression, and its scarlet eyes were fixed on Ning Yu as if he were looking at a dead man.

Ning Yu took a deep breath; he knew the real challenge had arrived. He mobilized the remaining energy within his body, and golden light shimmered around him, illuminating the battlefield shrouded in darkness.

"Come on!" Ning Yu roared, taking the initiative to face the giant monster.

An earth-shattering battle unfolded amidst the ruins, with Ning Yu single-handedly confronting countless monsters and the terrifying colossal monster. Every punch he threw, every burst of energy he unleashed, felt like a challenge to the limits of death.

"Boom! Boom! Boom!"

Violent explosions echoed one after another, and the entire territory trembled as if it were about to collapse at any moment.

Just when Ning Yu was about to give up, he suddenly sensed a peculiar energy fluctuation. This energy fluctuation was very weak, but it was extremely attractive, like a beacon in the darkness, guiding him in the right direction.

Ning Yu's heart skipped a beat. Could this be the source of those monsters?

He endured the excruciating pain in his body and rushed towards the direction from which the energy fluctuations were coming. Along the way, he didn't know how many monsters he killed or how many injuries he sustained, but he never gave up, because he knew he had found hope.

Finally, he arrived at the source of the energy fluctuations. It was a dilapidated building, which had survived countless battles and was now emitting a faint light.

Ning Yu cautiously entered the building. In the ruins, he found a metal box. The surface of the box was covered with ancient runes and emitted a strange energy fluctuation. It was this energy fluctuation that attracted those monsters!

Ning Yu was overjoyed. He knew he had found the source, and as long as he destroyed the box, he could resolve the crisis.

He reached out to open the box, but just then, an old voice suddenly rang in his ear: "Don't open it..."

The voice was weak and ethereal, yet it seemed to possess a power that pierced the soul, causing Ning Yu's hand to suddenly freeze. He looked around; the ruins were deserted, except for the even brighter light emanating from the metal box.

"Who is it?" Ning Yu asked in a deep voice, clenching his fists warily. Golden energy swirled around him, ready to deal with any new threat at any moment.

There was no answer, only that aged voice spoke again, tinged with a barely perceptible sadness: "Child, that box is..."

The sound abruptly stopped, as if a force had suddenly severed it. Ning Yu's heart skipped a beat. His intuition told him that the owner of the voice had some close connection with the box, and that the secrets hidden within the box were far more complex than he had imagined.

The monster's roar grew closer, and time was running out for him. A resolute glint flashed in Ning Yu's eyes. Rather than waiting to die, he would fight back. Ignoring the mysterious voice, he gathered all his strength, and golden energy transformed into a beam of light, slamming it fiercely into the metal box.

A deafening explosion echoed through the sky, the shockwave leveling the surrounding ruins. Ning Yu was thrown back, crashing heavily to the ground, spitting out a mouthful of blood. But ignoring his injuries, he struggled to lift his head and look in the direction of the explosion.

The once gleaming metal box had vanished, replaced by an eerie stillness. The frenzied monsters, seemingly lost and aimless, wandered aimlessly before receding like a tide, disappearing into the darkness as if on cue.

The territory was saved.

Ning Yu forced himself to his feet, his brow furrowed as he stared in the direction the monster had retreated. He knew this crisis was only temporarily averted; a greater mystery was just beginning to unfold. That mysterious voice, the secret hidden in the box, and...

"Beep! Abnormal energy fluctuations detected around the host. System upgrade imminent..."

A mechanical voice rang in Ning Yu's mind, cold and emotionless, yet it exploded in his ears like a thunderclap.