They had departed just after dawn.
The morning sky was dull gray, thick with lingering ash and floating particulates that glowed faintly in the light—residue of the fractured world above. The Phoenix Rig rumbled across the cracked main road, weaving through the skeletal ruins of warehouses, factories, and abandoned checkpoints.
Lu Zhen kept one hand on the steering grip, his HUD synced with the vehicle's internal map. The coordinates Lin Xia discovered from the emergency map terminal pointed them toward a former industrial hub on the city's eastern edge—now a ghost sector shrouded in dust.
"Metro D-7 should be ahead," Yue Fei said from the passenger seat, checking her blade. "If the entrance isn't caved in, it'll be one of the oldest sub-surface transit networks still intact."
Lu nodded. "Do we know how deep it goes?"
"Reports said some lines reached emergency bunkers outside the city," she replied. "Old military infrastructure buried beneath commuter stations. Not all of them got used, though."
As they neared the marked location, the terrain changed. Cracked highways gave way to a sloped road flanked by overgrown pillars and fractured rail signs. The remnants of barricades and rusted transport shuttles lay scattered near the tunnel mouth like bones.
The HUD pinged softly.
[Location Match – Metro Line D-7 Access Ramp Located]Status: Entry PossibleDistance to Tianlei (via estimation): 113.2 km
The Phoenix Rig came to a halt.
Yue stepped out first, scanning the tunnel's shadowed maw with narrowed eyes. "We go in on foot from here. No telling how narrow it gets inside."
Lu stepped out beside her, gazing into the darkness.
And so, without fanfare, they prepared to descend.
The entrance to Metro D-7 loomed like the open mouth of something ancient and waiting.
The ramp was wide—surprisingly intact for something decades old. Cracks lined its concrete slope, but the rebar hadn't yet given way. Vines hung from above, some dead, others pulsing faintly with bioluminescence like veins of an alien system.
Lu Zhen stood outside the Phoenix Rig, HUD active, running one final check.
Vault: 9.72 m³ / 10.00 m³Crafting Materials: StableEnergy Reserves: 87%System Ping: Weak – No Hostile Signatures
Yue Fei approached, gear secured across her body. "We go in ten meters, park, and seal. From there… we walk."
Lin Xia adjusted her backpack, the keychain fox now tied neatly to her side zipper. "This place gives me chills."
Lu looked toward the sloping entrance. "That's the point."
They boarded the RV and drove slowly into the tunnel. The rig's reinforced tires rolled over the concrete incline with a low rumble, and the interior lights dimmed as natural sunlight disappeared. After descending about fifty meters in, they found a split alcove meant for maintenance stops.
"This is far enough," Yue said, stepping out first with her blade drawn. "Anything deeper, we risk getting trapped."
Lu shut off the engine and activated external scan locks. The HUD marked the vehicle's location with a pulsing blue dot—Fallback Point: Phoenix Rig.
He set additional precautions: a proximity alarm rigged from scrap coils and a low-tone tripwire audio alert. If anything approached within a five-meter radius of the RV, the system would ping his HUD with a silent pulse. The RV also had enough fuel to restart and reach them automatically if pinged.
Before they left, he crafted several basic items:– 9mm ammo x4– Knife upgrade: reinforced grip wrap– Light module from scrap wiring + LED lens
He handed the modified utility knife to Lin Xia. "It won't stop a beast, but it'll keep one off your throat."
She nodded, tightening her grip.
Then they walked—carefully, slowly, with every footstep echoing like a warning shot into the abyss.
At 500 meters in, the walls narrowed. The lights overhead were long dead, but Lu's light module cut a clean cone through the dust. The smell grew dense—rust, oil, mold. Strange black vines threaded the ceiling like veins, some still pulsing faintly with iridescent glow.
Every so often, they heard water dripping—or maybe it wasn't water. Metallic echoes ricocheted off the curving tunnel like whispers that didn't want to leave.
Lu occasionally reached out, marking walls with glowing chalk, their blue slashes standing out in the dark like waypoints to the surface.
At the 1-kilometer mark, Lin Xia stumbled.
"Hold up," she said, pressing her back against the wall. "My head… feels off."
Lu stepped over, checking her vitals through HUD overlay.
"Air's stale down here. Try breathing in slow bursts. Four seconds in, six seconds out." He handed her a water canister.
She nodded, following the breathing rhythm.
"It's okay," Lu added, keeping his voice steady. "It's normal. Even before all this, people had panic reactions underground."
They waited a minute before continuing.
At 2 kilometers, they reached an old terminal station. The platform was cracked and crooked. What used to be a vending machine lay in pieces, and a security bot stood collapsed in the corner, rusted shut.
Lu approached a flickering control terminal. Surprisingly, it still had power.
[System Link Established – Restricted Log Access]Decrypting…File Recovered: Blueprint – Modular Rail Crawler v0.9Status: Blueprint saved (Locked – Requires Craft Lv.3)Description: Single-rider utility rail vehicle. Speed adjustable. Cargo capacity 0.8m³Note: Partial schematic integrity allows early access once skill threshold is met.
Lu's eyes narrowed. "Now this… this could be useful."
From the terminal's side panel, he found a half-melted datapad. Once connected to the HUD, it began syncing automatically.
[Data Log Recovered – Evacuation Report #221-B]— Evacuation route was overrun 3 days after rift appeared.— EXO SHELL MODEL A-04 deployed to Sector B, status: lost.— Civilian count: 27. Survivors extracted: 3.— Pathway deemed unstable. Log ends.
He read silently, then turned to the others. "There was a military deployment here. They sent an exoshell unit down the line."
"Think it's still down there?" Yue asked.
"If the tunnel hasn't collapsed? Maybe."
Lin looked uncertain. "Or maybe whatever stopped it… is still down there too."
They pressed deeper.
At 3 kilometers, they found a side chamber. Inside was a locker marked Transit Guard.
Yue forced it open with her blade. Inside was a rusted baton, a cracked helmet, and a locked container.
Lu bypassed the lock with a makeshift wire probe. Inside?
[Blueprint Partial – Blade Attachment Upgrade]Status: Incomplete (35%)Function: Tactical melee extension for exo-arm or modular mountCrafting Requirement: Lv.3, Tier 2 materialsNote: Suitable for custom modular weapon path
He nodded in satisfaction. "This will be important later."
As they walked, Lu ran a quick HUD diagnostic. He activated terrain mapping based on proximity sensors, adjusting environmental filters. A faint red line traced their steps behind them. Every 500 meters, a new anchor point was logged.
"Auto-ping fallback activated," he murmured. "If signal drops, HUD will route us to last stable marker."
At 4.5 kilometers, the tunnel dipped. The ground became uneven, wet with condensation. Light from their modules reflected off metal plates buried in the concrete—probably reinforcements for train stabilization.
Then, at 5 kilometers, they stopped.
Ahead, the tunnel opened into a larger chamber—an old switching junction, partially collapsed. Crushed crates and deformed rail carts lay scattered. The silence here was heavier. Lingering. Watching.
Lu raised a hand. "This is the limit. We mark this… then turn back."
Yue agreed. "The air smells off. We go further, we risk being trapped."
Lin looked around nervously. "I feel like we're being watched."
Lu marked the wall with two diagonal slashes. Then paused.
His eyes caught a broken rail sign, rusted and crooked. Its label, barely visible, read: "D7-EXT—Emergency Exit B."
He whispered, "We'll come back for this."
On the way back, no one spoke much. But everyone walked faster.
At 3 kilometers, the datapad began flickering again—picking up residual signal.
[Warning – Passive Echo Detected]Unknown energy reading: Static pulse, fluctuating.Threat: Undetermined.
Lu clenched his jaw. "Something's active here. Maybe just residual energy… maybe not."
By the time they reached the Phoenix Rig, two hours had passed.
Lin collapsed into her seat. "That was the most terrifying walk I've ever taken."
Yue leaned against the wall. "And it won't be the last."
Lu looked at the glowing marker on his HUD.
Phoenix Rig – Location LockedRoute to Base Tianlei – Approx. 113.2 km remaining
He whispered, more to himself than anyone:"We're not alone down here. But we're not weak either."
Outside, the tunnel stayed silent. But in the distance, something… echoed.