Puddles of rainwater mixed with soot reflected the faint, flickering beam of an emergency spotlight far down the tunnel. The night air smelled of ozone and rusted iron, mingling with the ragged, heavy breathing of Zulfa and Naya. Before them, the inactive underground railway tracks stretched out like a dead labyrinth of steel. But tonight, that labyrinth was alive with an impossible threat.

"Naya, don't move!" Zulfa whispered sharply, his eyes locked on a thick shadow slithering along the rails.

The entity—a humanoid silhouette textured like condensed oil smoke—let out a shrill hiss. Its sound resembled rusted metal scraping across glass. A pair of glowing red eyes in its head stared straight at Naya, who was huddled weakly on the slippery rails. Seeping oil and moss made the footing there dangerously treacherous.

Naya winced, clutching her ankle, which she had sprained when she slipped earlier. "Zulfa... it's... it's getting closer! I can't move my leg!"

The shadow creature lunged. Its speed was extraordinary, tearing through the damp air with a swipe of smoky claws that kicked up black dust.

"Damn it!" Zulfa muttered. Instead of retreating, his body surged forward instinctively.

He knew that running on these slick rails would only leave them cornered and caught. This creature wasn't merely a ghost; its form possessed a specific physical density, meaning it was bound by the laws of energy. And in this place, energy was both a weakness and a weapon.

Thud!

Zulfa tackled forward, shoving Naya harder against the concrete tunnel wall, while the shadow's claws whipped past a mere inch from his shoulder, tearing his cloth jacket and leaving a scorched trace behind.

"Zulfa! Are you insane?!" Naya screamed in panic, gasping for breath as she fought the pain in her leg.

"Shut up and trust me!" Zulfa shot back quickly, his own breathing sharp and ragged.

His brain spun at 1,800 kilometers per hour, flashing back to the underground architectural schematics he had studied from the city's old utility maps.

Sector Four distribution substation... The old line's emergency transformer... Where was it positioned? Zulfa thought, his eyes sweeping the concrete walls packed with aged cables as thick as a grown man's arm.

The shadow creature spun in the air with terrifying acrobatic precision, landing back on the iron rails. Thick smoke billowed from its body, forming phantom wings that stretched wide. It prepared for a second, far more lethal strike.

"Naya! Listen to my voice!" Zulfa shouted over the roaring wind of the tunnel, trying to draw the monster's attention. "To your right, there's a rusted steel panel box with a red lightning bolt symbol on it. Can you see it?"

Naya, tears nearly spilling from sheer terror, turned her head with great effort toward where he pointed. Amidst the darkness, an iron box embedded in the wall with peeling paint came into faint view. "T-that? Yes, I see it! But the lock... it's padlocked!"

"Don't open the lock! Just look for the manual circuit breaker lever underneath the box, the one with the thick orange cable!" Zulfa instructed firmly, stepping in front of Naya to act as a living shield.

The creature snorted, emitting a high-frequency squeal that made their ears ring. It rocketed forward, charging straight at Zulfa with its sharp claws bared.

"Now, Naya! Pull the lever down right now!" Zulfa yelled just as the shadow struck.

Click!

The harsh sound of grinding metal echoed through the narrow tunnel. Instantly, all the emergency lights flickered violently before dying out completely. Pitch darkness swallowed them whole, but only for a fraction of a second.

Zulfa had calculated everything. By forcing that emergency lever, he triggered a manual short circuit in the high-capacity transformer located directly beneath the rail bed. Wild electrical currents of thousands of volts leaped out from frayed cable splices, racing along the wet iron rails.

BZZZZT—!

A blinding flash of brilliant blue light tore through the tunnel. A massive electromagnetic shockwave exploded into the air, carrying a colossal electrical charge that slammed directly into the shadow entity at its core.

"Arghkh...!"

The creature shrieked, a high-pitched sound akin to metal being forced to bend. Its entire smoky black body began to convulse violently. The unstable electromagnetic field disrupted its shadow particle structure, fracturing the dense molecular bonds that held its form together.

Naya covered her eyes with both hands, blinded by the incandescent sparks flashing wildly around the rails. "Zulfa! Did it work?!"

"Hold on a second longer!" Zulfa shouted, shielding his face with his jacket sleeve from the hot wind generated by the short circuit.

Within seconds, the screech faded. The humanoid silhouette that had looked so solid and terrifying softened, melting like wax exposed to an intense flame. Its shape dissolved, running rapidly down onto the concrete surface and puddling water until finally leaving behind only a pool of jet-black fluid that smelled like burning tar.

The tunnel fell silent once more, leaving only the faint hum of burning cables and the ragged breathing of the two teenagers in the dark.

Zulfa lowered his arm, exhaling a long, heavy breath. Sweat streamed down his temples. His legs felt weak, but he forced himself to step closer to the remnants of the puddle.

"Z-Zulfa, is it gone?" Naya asked tremulously, trying to drag herself away from the pool of black tar.

"Yeah. For now," Zulfa answered softly. He crouched down, observing the dark liquid as it began to cool and dry over the concrete.

In the center of the slowly solidifying tar puddle, something caught the dim, lingering light of Zulfa's fallen smartphone near the rails. It was a small, thin rectangular object made of dark metal, etched with an intricate, elegant, and expensive-looking motif of a coiled silver serpent.

Zulfa reached out, picking up the object with the tips of two fingers to avoid the remaining fluid. He lifted it close to his phone screen.

"An access card...?" Zulfa muttered, narrowing his eyes.

Stamped across the metal card's surface was a corporate logo well-known among the city's elite, though entirely out of place in a derelict spot like this:

Aethel Corp. Urban Infrastructure & Maintenance Contractor.

Naya, who had managed to crawl closer, caught sight of the engraving on the card. Her eyes widened completely. "Aethel Corp? Wait... isn't that the massive private corporation handling the downtown district renovation project? What is something of theirs doing inside a shadow monster?"

Zulfa stood up slowly, slipping the silver-serpent-etched access card into his jacket pocket. His gaze sharpened on the darkening end of the tunnel.

"Because," Zulfa said quietly in an icy tone, "that thing back there wasn't from another dimension, Naya. It was manufactured."

What do you think connects Aethel Corp's urban renewal project to these engineered shadow creatures lurking beneath the city?