Stepping through the threshold of The Vault was like stepping into a void.

There were no shelves, no counters, no walls. There was only suffocating, absolute darkness. Suspended in the center of this boundless nightmare was a single, lonely oil lamp, its flame casting a pathetic halo of light barely the size of a human palm.

Jax waved his hand through the air, his fingers grasping at nothing but empty cold.

“This is a shop?” Jax muttered, his voice swallowed by the silence. “Where’s the merchandise?”

As if responding to his thought, the flame flickered. A crimson pouch materialized from the gloom, hovering directly beneath the lamp.

Jax reached out and grabbed it. A holographic window popped up instantly.

[Item: Frenzy Serum] [Price: 100 Cores] [Effect: Increases Defense Tower Attack Power and Attack Speed by 200%. Duration: 60 Minutes.] [Purchase?]

Jax’s eyes widened. A surge of adrenaline cut through his exhaustion.

“Two hundred percent? For an hour?” He grinned savagely. “This is exactly what we need to survive this hell.”

He didn’t hesitate. He slammed his finger on the [Confirm] button.

Instantly, a glowing question mark appeared over the silhouette of his Sentry Tower in his mental interface. He selected the tower nearest the breach.

Hummmmm.

Outside, a deep mechanical resonance vibrated through the ground.

The Sentry Tower groaned as its internal gears shifted into overdrive. The structure seemed to telescope upwards, steam venting from its joints as the mechanism accelerated to a blur.

Thump-thump-thump-thump!

The firing rate exploded. It wasn’t a rhythmic beat anymore; it was a continuous roar of heavy artillery.

Arrows turned into streaks of light, raining down on the encroaching horde with terrifying precision. Because the Sandworms were packed so tightly, the tower didn’t even need to aim. Every bolt punched through a carapace, pinning insects to the ground or blowing them apart.

For thirty minutes, the canyon echoed with the screeching of dying monsters and the relentless pounding of the tower.

The tide of black shells began to recede. The frenzied firing had broken their morale.

Finally, the last screech died out. The canyon fell silent.

The Sentry Tower shuddered one last time as the Frenzy Serum wore off, its mechanism winding down to its normal, idle hum.

Jax, illuminated by the dying embers of the bonfire, scanned the perimeter. Nothing moved. The ground was carpeted in twisted insect corpses.

“We made it,” Jax exhaled, the tension leaving his body in a rush. “Hardest fight of my life.”

He didn’t waste time looting Cores. He sprinted toward the Bastion where he had dragged Barney.

The giant was in bad shape. White froth bubbled at the corners of his mouth, and his eyes were rolled back in his head.

Jax pressed two fingers to Barney’s neck. “Pulse is weak… but he’s breathing.”

He scrambled into the Bastion and hauled out a massive waterskin.

Jax knew Sandworm biology. Their venom was a neurotoxin, nasty but rarely fatal if treated quickly. The cure was simple: flush the system.

“Drink, big guy. Come on.”

He tilted Barney’s head back and poured water into his mouth, washing away the foam.

Barney choked, swallowed, and then retched violently.

Jax didn’t stop. He kept pouring, forcing the giant to hydrate. Drink, vomit. Drink, vomit.

It was a messy process, but effective. By the time the waterskin was empty, the color had started to return to Barney’s grey face, and his pulse hammered with a steady rhythm.

Jax collapsed against the cool concrete wall, drenched in sweat, gasping for air.

Barney’s eyelids fluttered. He groaned, shifting his massive weight.

Jax let out a breathless chuckle. “You brat. I told you to run, but no, you had to play hero. Now look at you. Hope you enjoyed the free bath.”

Barney didn’t open his eyes, but he mumbled something in his delirium.

“Jax… I’m a man… Can’t leave a teammate behind…” A pause. “You’re my brother…”

Jax’s smile softened. He reached out and patted the giant’s cheek.

“Yeah. You did good, Barney. The worms are dead. Sleep now. I’ll make you whatever you want for breakfast.”

Within seconds, Barney’s breathing deepened into a rhythmic, thunderous snore.

Jax stood up, his legs shaking, and turned his attention back to his new asset: The Vault.

He still didn’t fully understand how it worked. He approached the pitch-black building and placed his hand on the doorframe, focusing his mind on the oil lamp inside.

[System Alert: Refresh Shop Inventory? Cost: 100 Cores.]

“Ah,” Jax realized. “It’s a gacha mechanic. Costs Cores to buy, costs Cores to reroll. Expensive habit.”

He looked around the platform. It was a disaster zone. Debris, corpses, and ichor covered every inch of ground. The darkness was still thick, and exhaustion was pulling at his eyelids like lead weights.

“Forget it. Cleaning up the battlefield can wait until sunrise.”

He leaned against the Sentry Tower, resting his hand on the cold metal. To his surprise, a small status bar appeared.

[Repairing… Integrity +1…]

“It’s healing?” Jax blinked. “Why is it repairing itself?”

He jogged over to the perimeter wall. Several sections had been chewed down to the rebar, their integrity well below 50%. But they, too, had a faint shimmer of restoration.

Jax turned to the central Bastion and placed his palm on a support pillar.

[Tier 1 Bastion] [Integrity: 500/500] [Status: Active] [Passive Effect: Structural Regeneration Field. Slowly repairs all allied structures within range.] [Warning: If the Bastion is destroyed, regeneration ceases, and no new structures can be built.]

“I get it now,” Jax murmured, a wave of realization washing over him. “The Bastion isn’t just a concrete tent. It’s the Command Center. It’s like the Construction Yard in Red Alert.”

It wasn’t a useless hunk of concrete. It was the heart of his base. As long as the Bastion stood, he could rebuild. If it fell, it was Game Over.

“Good to know,” Jax whispered. He checked the other tower. It was down to 40% integrity but ticking upward steadily.

His anxiety melted away. He sat down next to the sleeping Barney, listening to the hum of the base repairing itself.

Jax didn’t remember falling asleep.

One moment he was watching the integrity bars tick up, the next, warmth was pressing against his eyelids.

He opened his eyes. The sun was cresting the canyon walls, bathing the outpost in golden light.

The scene revealed by the daylight was gruesome. The canyon floor was a slaughterhouse, layered thick with Sandworm carcasses. But inside the base, things were peaceful.

Jax stretched, surprised to find his own body feeling remarkably light. The poison was gone, and his wounds had scabbed over rapidly.

Must be that Augmentation Serum I took during the tutorial, he mused. My recovery rate is insane.

He checked Barney. The giant had several nasty lacerations, but Jax’s triage had done the trick. The only concerning injury was a deep gash on his lower back, exposing muscle and flirting with the bone.

“We need to get him to Outpost 15,” Jax noted grimly. “That needs stitches and real antibiotics.”

He stood up, intending to harvest some Cores before they left.

“Jax! Hey! Are you alive in there?”

A shout echoed from the valley entrance.

Jax turned to see a figure silhouetted against the morning sun. It was Silas.

The older man jogged into the valley, but froze when he got close enough to see the platform. His jaw dropped.

He stared at the mountain of dead Sandworms piling up against the walls. Then his eyes traveled up, locking onto the two imposing Sentry Towers and the ominous black block of The Vault.

“Holy…” Silas stammered, walking up the ramp with wide eyes. “You… you did all this? Those towers are yours?”

Jax nodded, weary but alert. He gestured to the carnage. “If you’re willing to help me clean up the battlefield, I can pay you.”

Silas shook his head frantically, waving his hands. “Put your Cores away. I’m not here for money.”

He looked at Jax with a newfound respect, bordering on awe. “Every outpost got hit hard last night. Bodies everywhere. I just came to check if you were… well, dead. I didn’t expect to find this.”

He rolled up his sleeves and stepped over a dead worm. “You rest, Jax. You look like hell. Let me handle the harvesting.”

Jax didn’t argue. With Silas taking over the grunt work, he finally allowed himself to sit back down. The Bastion might repair the buildings, but only rest would repair him.