Morning in the Sump didn't arrive with sunlight. It arrived when the bioluminescent moss on the ceiling turned a slightly brighter shade of sick green.

  I woke up because a drop of condensation fell directly onto my forehead. I groaned, rolling off the canvas cot. The air was thick, heavy with the smell of stagnant water, machine oil, and the acrid, lingering smoke from Rax’s ancient kerosene stove. My clothes felt clammy, sticking to my skin like a second layer of sweat.

  I sat up and reached for my boots. Shake. Tap. Tap. A finger-length centipede with pale, translucent legs fell out of the left boot and scurried into a crack in the brickwork. "Morning to you too," I muttered, jamming my foot inside.

  I walked over to the edge of the drainage canal. The water was black and moved sluggishly. I cupped my hands and splashed the freezing liquid onto my face. It smelled faintly of iron and sulfur, but it woke me up. I looked at my reflection in the dark water. The clean-shaven, optimistic student from the Academy was gone. The man staring back had hollow cheeks, dark circles under his eyes, and a layer of grime that seemed permanently etched into his pores.

  "Food's up," Rax called out from the campfire. "And by food, I mean hot sludge."

  I walked over. Amelia was already there, helping Rax ladle the green moss soup into tin bowls. She looked better today—her color had returned, though she was still thin. She handed me a bowl. Floating in the green muck were chunks of grey, fibrous meat.

  "What is it today?" I asked, poking a piece with a rusted spoon. "Salted cave-rat," Rax grinned, tearing a strip off a dried carcass hanging by the fire. "Chewy. Salty. High protein. In the Sump, this is practically steak."

  Amelia took a small bite and wrinkled her nose. "It tastes like a leather shoe that walked through a salt mine."

  "Luxury," Rax laughed, his mechanical eye whirring. "Eat up, princess. You need the strength."

  We ate in a comfortable silence, the only sounds being the scraping of spoons and the distant drip-drip of the tunnels. It was a strange, quiet moment of domesticity in the middle of a war zone.

  I looked over at the Centurion. It stood silently in the shadows, a headless, armless giant. "It's a sitting duck," I said, breaking the silence.

  Rax looked up. "It runs fine now."

  "It runs," I agreed. "But it can't reach. If the Truth Mage comes back, he won't stand on the ground. He'll fly. Or he'll stand on a rooftop three blocks away and rain fire on us until we cook inside that chassis."

  Amelia stopped eating. She was holding a long, rusted iron skewer she had been using to toast a piece of bread. She looked at the sharp point, lost in thought.

  I followed her gaze. I stared at the heavy iron spike. "Rax," I said slowly, putting my bowl down. "Deep in the old mining sector... did they leave any of the pneumatic equipment behind?"

  "Pneumatic?" Rax frowned. "You mean the air-driven stuff? Yeah. The dwarves left tons of it. Heavy, rusted junk. Why? You want to open a quarry?"

  I took the skewer from Amelia's hand. I held it up, aiming it at the far wall like a spear. "No," I said, my mind already racing with schematics. "I want to take the rock breakers. The ones used to drive railway spikes into solid granite."

  "And then?"

  "And then I want to mount one on the Centurion's shoulder." I looked at the thick iron skewer. "If a machine can drive a spike into stone, it can drive one through a magical barrier. We don't need lasers, Rax. We need a really, really big nail gun."

  The walk to the deep mining sector took an hour. As we ventured deeper, the brickwork of the sewers gave way to rough-hewn natural rock. The air grew cooler and fresher here, fed by natural vents.

  The ceiling was covered in vast colonies of bioluminescent fungi. They glowed with a soft, ethereal blue light, creating the illusion of a starry night sky underground.

  "It's beautiful," Amelia whispered, looking up.

  "It's a lot better than the smell back at camp," I admitted.

  We walked side by side, our boots crunching on loose gravel. "It reminds me of home," Amelia said softly. "Not the dampness. But the wind. In Xinjiang, the wind never stops. It scours everything clean. The air always smells like dust and sage."

  A case of literary theft: this tale is not rightfully on Amazon; if you see it, report the violation.

  "I miss the sun," I said. "Real sun. Not this blue fungus."

  "We'll see it again," she said, bumping her shoulder gently against mine. "Once we fix your giant nail gun."

  We found the equipment graveyard in a collapsed side tunnel. It was a pile of rusted history. Mine carts, pickaxes, and twisted rails lay in heaps. And there, half-buried under a pile of shale, was the prize.

  A "Grumman & Sons" Pneumatic Rock Breaker. It was massive—a cylinder of cast iron as thick as my thigh, with a piston rod the size of a fist. It looked like a cannon that had lost its wheels.

  "Heavy," Rax grunted, kicking it. "The seals are probably dried out."

  "We can grease the seals," I said, kneeling down to inspect the air intake valve. I brushed away a nest of glowing beetles that scattered indignantly. "This is it. The Riveter."

  Building a weapon in a high-tech lab is science. Building a weapon in a sewer is an exercise in frustration.

  We dragged the heavy breaker back to camp and hoisted it onto a workbench. My plan was simple: connect the breaker's air intake to a high-pressure compressor driven by the V8's accessory belt. Then, build a gravity-fed hopper that would drop heavy iron railway spikes into the chamber one by one.

  "Damn it!" I threw my welding torch down. "What's wrong?" Amelia asked. She was sitting on a crate, watching me work.

  "The nozzle is clogged again," I growled, wiping sweat from my forehead. "The gas mix is dirty. Every time I try to weld the hopper, it sputters out."

  I grabbed a thin needle to clean the tip, my hands shaking slightly from fatigue. Amelia stood up. She walked over to the pile of scavenged railway spikes I was prepping. They were covered in fifty years of flaking orange rust.

  "I can't weld," she said. "But I can clean."

  She held up a rusty spike. A small, concentrated vortex of wind formed around her hand. It spun violently, like a miniature sandblaster. Whirrrrr. Red dust flew into the air. When the wind stopped, the spike in her hand was stripped to bare, grey metal.

  "Show off," I grinned.

  She laughed, but then she wiped her face. She had forgotten that the rust dust had to go somewhere. She now had a distinct reddish-orange mask of iron oxide covering her nose and cheeks. She looked like a tribal warrior, or a very confused red panda.

  "You have a little something..." I pointed to my own face.

  She rubbed her cheek, only smearing it further. "Is it bad?"

  "It's a look," I chuckled. "Very industrial chic."

  We spent the next six hours like that. I welded the gravity hopper—a crude, funnel-shaped metal box—while she stripped the ammo. Rax sharpened the tips of the spikes on a grinding wheel, sending showers of yellow sparks into the gloom.

  It wasn't romantic in the traditional sense. We were filthy, tired, and building a machine designed to kill. But there was a rhythm to it. A shared purpose. We were turning rust into survival.

  By evening, The Riveter was mounted. It looked hideous. Welded to the right shoulder of the Centurion, it looked like an oversized, industrial tumor. The gravity hopper stuck up like a chimney, filled with twenty sharpened railway spikes. A thick rubber hose connected it to the engine bay.

  "Range test," I announced.

  Rax had set up a target fifty meters down the main tunnel: a heavy oak door reinforced with iron bands, propped up against the stone wall.

  I sat in the cockpit. I didn't need to turn on the main engine; the auxiliary compressor had enough pressure in the tank for a few shots. I lined up the crude iron sights welded to the barrel. I pulled the cable trigger.

  THUNK!

  It wasn't a bang. It was a deep, resonant sound of heavy metal striking metal, followed by the hiss of escaping air. The recoil rocked the chassis slightly.

  Fifty meters away, the heavy oak door didn't just break. It exploded. A fist-sized hole appeared in the center. But the spike didn't stop there. CRACK.

  We walked over to inspect the damage. The railway spike had punched through four inches of reinforced oak, continued its flight, and embedded itself six inches deep into the solid brick wall behind it. The metal shaft was still vibrating, humming with kinetic energy.

  Rax let out a low whistle. "That's not a gun. That's a spear thrower."

  "It's slow," I critiqued, running my hand over the splintered wood. "Maybe two shots a second. And the accuracy is terrible beyond a hundred meters."

  "It doesn't matter," Rax said grimly. "If that hits a mage's shield, the kinetic energy alone will knock him flat. If it hits flesh..."

  He didn't finish the sentence.

  Amelia was staring at the spike embedded in the wall. The playful mood from the afternoon was gone. Her face, still streaked with rust dust, was pale. She reached out and touched the cold iron. "We're going to use this on people," she whispered. It wasn't a question.

  I stood beside her. I wanted to tell her we wouldn't. I wanted to tell her it was just for intimidation. But I couldn't lie to her. Not anymore.

  "We are fighting an Empire, Amelia," I said quietly. "They have fireballs that can melt tanks. They have wind blades that can slice bone. We have this."

  I looked at the brutal, jagged hole in the wood. "We aren't just trying to kill them. We need to terrify them. We need them to look at this machine and decide that the bounty isn't worth it."

  She nodded slowly, pulling her hand back. "I know. I just... I never thought I'd be the one holding the hammer."

  "You aren't," I said firmly. "I am. You just keep the engine running."

  Night settled over the Sump. The air compressor had cooled down. Rax and the others were asleep, their snores echoing softly in the chamber.

  I sat by the dying fire, my notebook open on my knee, calculating the air pressure requirements for a higher fire rate. The Riveter was functional, but it was hungry.

  Clang. Clang. Clang. Clang-clang.

  I froze. The sound came from above. It was the heavy iron manhole cover that led to the surface alleyways. Someone was hitting it with a metal bar. Three long strikes. Two short.

  It wasn't the erratic banging of a Guard patrol. It was rhythmic. Deliberate. It was a code.

  Rax sat up instantly on his cot, his hand already on his pistol. He looked at me, his mechanical eye glowing red in the dark. "That's the signal," Rax whispered.

  "The Black Market?" I asked, closing my notebook.

  "The Broker," Rax corrected, standing up and checking his weapon. "He's early. And if he's knocking this loud, he's got news we need to hear."