The Sump was not a place for the living.

  Located deep beneath the tangled roots of the Rust Yard, it was a colossal, abandoned maintenance station for the city’s ancient sewage and drainage systems. It smelled of wet stone, dead rats, and centuries of stagnant water.

  It was perfect.

  The Centurion Siege Walker limped into the cavernous underground chamber, its metal feet splashing heavily into the shallow, murky water that covered the floor. The echo of its movement was dull and heavy, swallowing the usual sharp clang of metal.

  "Cut it," I whispered, my voice raspy from smoke inhalation.

  Amelia didn't respond verbally. She just let her hand drop from the copper distributor.

  The V8 Mana-Combustion Engine let out one final, shuddering gasp. The pistons knocked once, twice, and then the beast died.

  Silence rushed back into the chamber, heavy and oppressive, broken only by the tink-tink-tink of cooling iron and the hiss of boiling water escaping the radiator cap.

  I unbuckled my harness. My hands were shaking so badly I could barely work the clasps. My muscles felt like they had been shredded by a cheese grater. Every pull of those hydraulic levers had been a battle against physics, and physics had fought back hard.

  "Amelia?" I called out, turning to the rear seat.

  She didn't move. She was slumped forward against the safety bar, her head hanging low. Her face was the color of old parchment. A thin trickle of blood ran from her left nostril, stark red against her pale skin.

  Panic, cold and sharp, pierced through my exhaustion.

  "Amelia!" I scrambled out of my seat, slipping on the oil-slicked deck. I unlatched her harness and pulled her limp body out of the cockpit. She was frighteningly light. Her skin was cold to the touch, clammy with a feverish sweat.

  "I got you," I grunted, jumping down from the chassis into the knee-deep water. I carried her toward the dry raised platform where Rax had set up a makeshift camp.

  Rax was already there, lighting a kerosene lamp. The warm yellow glow pushed back the shadows. "Is she...?" Rax asked, his mechanical eye whirring as it focused on her.

  "Mana exhaustion," I said, laying her gently on the cot. "She burned her core dry to keep that engine firing. She needs sugar. And water. Now."

  Rax nodded and tossed me a canteen and a package of high-calorie nutrient bars—the kind miners ate when they were trapped underground.

  I tore the package open and broke off a small piece. I lifted Amelia's head. "Come on," I whispered. "Eat. Just a little."

  Her eyelids fluttered. She groaned, a sound of pure misery. She took a tiny bite, chewing slowly, mechanically. Then she took a sip of water. Color didn't return to her cheeks immediately, but her breathing steadied. The terrifying stillness left her.

  "We pushed too hard," I muttered, wiping the blood from her nose with my sleeve. "I treated her like a battery."

  Amelia’s eyes opened a slit. She looked at me, her gaze unfocused. "Did we... win?" she croaked.

  "We survived," I corrected. "Go to sleep. I'll watch the door."

  She didn't argue. She was asleep before her head hit the pillow.

  I sat there for a long time, watching her chest rise and fall, holding the unopened nutrient bar in my grease-stained hand. I had built a monster to fight monsters. But if the cost of driving it was killing the only person who trusted me, then the design was a failure.

  Stolen novel; please report.

  "Julian." Rax's voice broke my trance. He was standing by the Walker, holding a large wrench. "You need to see this. It's bad."

  I stood up, my joints popping painfully, and walked over to the cooling machine. In the dim light of the lantern, the Centurion looked less like a conqueror and more like a car wreck.

  "The knees," Rax pointed with his wrench.

  I looked closer. The massive steel pins that held the knee joints together were scored with deep, jagged grooves. "No lubrication," I noted, running a finger over the metal shavings. "The friction welded them momentarily, then tore them apart. Another mile, and the legs would have seized solid."

  "That's the least of it," Rax walked to the rear. "Look at the heart."

  I climbed up to the engine deck. The V8 was a mess. Oil was splattered everywhere. I pulled the dipstick. Instead of dark, golden oil, the fluid dripping from the stick was a thick, milky-brown sludge.

  "Forbidden milkshake," I sighed, wiping it on a rag.

  "What?" Rax asked.

  "Water in the oil," I explained. "The head gasket blew. The explosion in the cylinders was so violent, and the heat so intense, that the seal between the engine block and the cylinder head warped. Cooling water leaked into the oil system."

  "Can we fix it?"

  "We can replace the gasket," I said, looking at the dead engine. "But it will happen again. And again."

  I kicked the iron railing in frustration. "The problem isn't the engine. It's the connection. We are connecting a high-speed, explosive rotary engine directly to heavy, static limbs. There is no give. No slip. Every time I pull a lever, the shockwave travels straight through the metal. It tears the gaskets, shreds the hoses, and grinds the gears."

  "We need a transmission," Rax said, using the word I had taught him.

  "Not just gears," I shook my head. "Gears have teeth. Teeth break. We need something fluid. Something that can absorb the shock of a fifty-ton stumble and convert it into smooth power."

  I looked at the murky water of the Sump. "We need a Torque Converter."

  An hour later, one of Rax's scouts—a nimble goblin named Skiv—came splashing into the hideout. He was breathless, his eyes wide.

  "Boss! The streets are going crazy!" Skiv chirped, scrambling up the platform.

  "The Guard?" Rax asked, hand moving to the heavy pistol at his belt.

  "They're gone. Pulled back to the Inner Wall," Skiv grinned, showing sharp teeth. "But the people... they're talking. Everyone saw it. The Iron Giant."

  He pulled a crumpled piece of paper from his pocket and smoothed it out on the crate we were using as a table. It was a crude charcoal drawing. It depicted a headless, blocky figure smashing a carriage.

  "There's a bounty," Skiv said. "Ten thousand credits for the 'Rogue Artificer' and his 'Abomination.' The Mage you embarrassed—Magister Thorne? He's furious. He says it's an affront to the Architects."

  "Thorne?" I looked up sharply. "Magister Thorne?"

  "Yeah," Skiv nodded. "Tall guy? Looks like he smells bad smells all the time?"

  I let out a short, dry laugh. Of course. Of all the mages in the city, I had to run over the one who taught "Theory of Magical Purity" back in my first year. The man who failed me because my mana circles weren't 'aesthetically pleasing.'

  "Ten thousand credits," Rax mused. "That's a lot of money in the Rust Yard, kid. People talk."

  "Let them talk," I said, staring at the drawing. "Fear is a currency. Hope is another. Right now, we have both."

  I pointed to the crude drawing. "They drew it standing tall. They didn't draw it running away. That matters."

  I couldn't sleep. While Amelia rested and Rax took the first watch, I sat under the flickering light of the kerosene lamp, a fresh stack of scavenged blueprints spread out before me.

  I looked at the damaged engine. I looked at the destroyed knees. The brute force method had worked for a breakout, but it wouldn't win a war.

  I took a piece of charcoal and started sketching.

  Problem: Jerky motion. Shock damage. Stalling the engine under load. Solution: Fluid Coupling.

  I drew a donut-shaped chamber. Inside, two fans faced each other. "The Impeller," I muttered, drawing the first fan, connected to the engine. "It spins and throws fluid outward." "The Turbine," I drew the second fan, connected to the legs. "It catches the fluid and spins."

  There is no metal-on-metal contact. Just oil, spinning violently, transferring power. If the legs get stuck, the turbine stops, but the engine keeps spinning. The oil just slips. No stalling. No snapping shafts. No blown gaskets.

  It was the difference between punching a wall and pushing a wall.

  I added a third component in the middle: The Stator. To multiply the torque. This would allow the Walker to crawl up steep inclines, to push through heavy barricades, to move with the smooth, unstoppable force of a hydraulic press rather than the jerky spasms of a dying animal.

  I looked over at Amelia. She was sleeping soundly now, her breathing deep and even. I owed her a better machine. One that didn't demand her life force just to take a step.

  I looked back at the drawing. "Sleep well, big guy," I whispered to the silent, cooling Centurion in the dark water. "When you wake up, you're going to have new legs."