The morning in the Rust Yard was choked by a freezing, dense fog. In this season, the mist always tasted of coal ash and the sour reek of the sewers.

  Our V8 Mana-Combustion Engine had just finished a night of cooling down. It was supposed to be the morning we put it to work, but when Foreman Rax kicked open the warehouse doors, he brought news cold enough to freeze blood.

  "The City Guard has cordoned off the perimeter," Rax said. His heavy mechanical leg thumped against the floor tiles, echoing dully in the quiet space. His face was darker than the fog outside. "They’ve set up barricades at every intersection leading to the Outer District. Truth Mages are going door-to-door looking for the 'Gas Bombers.' They’ve grounded all movement of heavy machinery and high-grade magical materials."

  The air in the warehouse instantly solidified. The dozen blacksmiths and laborers who had been moving steel beams stopped dead. A metal pipe slipped from someone's hands, hitting the ground with a deafening CLANG.

  "A blockade?" a heavily stubbled welder took a terrified step back. "If the Truth Mages catch us building this... this thing... they'll hang us from the city walls!"

  "I'm out!" a young apprentice threw his wrench down. "I just came here to earn meal money. I'm not dying for some crazy Academy student!"

  Panic spread through the crowd like a plague. A few men were already backing toward the rear exit.

  I looked at them. In that moment, I realized a harsh truth: a V8 engine, no matter how powerful, couldn't drive human hearts. If you don't know how to manage fear, the best engineering blueprints in the world are just scrap paper.

  I walked over to the main workbench and grabbed the heavy leather pouch I had received from Kaelen last night. SLAM. I threw the bag of 50,000 credits onto the iron anvil. The sharp, heavy clink of gold coins echoed through the cavernous room, instantly silencing the whispers.

  "Listen to me!" I raised my voice, the sound harsh in the freezing air. "The Guard has the district locked down. Even if you run out that door right now, you'll be rounded up as suspects and dragged to the dungeons for interrogation!"

  I pulled the drawstring on the pouch. The dull golden glow stung their desperate eyes. "We don't run." I grabbed a handful of credit chips and tossed them onto the anvil. "Anyone who stays and works today gets three months' wages paid in advance, right now. Consider it Danger Pay."

  The workers' eyes darted between the pile of gold and the foggy doorway.

  "Do you want to face the City Guard's spears with your bare hands?" I pointed to the far corner, where the massive, headless chassis of the Siege Walker sat in the shadows. "Or do you want to hide behind a fifty-ton steel monster and crush them? That is our only shield. Now, pick up your wrenches."

  Silence stretched for a few agonizing seconds. Then, the old welder stepped forward, his eyes on the gold, and picked up his tool. The instinct for survival—and the pull of cold, hard cash—overrode their fear of the mages.

  The immediate crisis was averted. Rax looked at me, a glint of genuine respect in his mechanical eye. "Nice trick, kid," he walked over, staring at the V8 engine that had roared to life the day before. "But we have a massive problem. You built the heart. How do you connect it to the Golem's legs? Gears? This engine spins so fast, the moment you engage the clutch, it will shred any gearbox we build into shrapnel."

  I didn't reach for chalk to draw dry diagrams of force vectors. For men like Rax, intuition beat equations every time. "Find me two bamboo tubes. One thick, one thin. And a length of sealed leather hose filled with water," I ordered.

  A few minutes later, I placed the crude contraption on the table. The thick and thin bamboo tubes were connected by the water-filled hose. Both had wooden plungers fitted inside.

  "Pascal's Principle," I said, placing my hand on the thin plunger. "Rax. Use your mechanical arm. Push down on the thick plunger. Give it everything you've got."

  Rax grinned. "Kid, this arm can crush granite." He casually slammed his metal palm onto the thick plunger. Creak. It didn't move. He paused, surprised, then gritted his teeth. The steam valves on his prosthetic hissed violently, and veins bulged on his human neck. He was pushing with all his might.

  And I? I was simply resting my thumb against the thin plunger. Due to the transmission of fluid pressure, the massive cross-sectional area of the thick tube dispersed his force, while the thin tube concentrated the pressure directly against my thumb. I didn't even break a sweat holding back the full strength of a cyborg enforcer.

  If you discover this tale on Amazon, be aware that it has been stolen. Please report the violation.

  Rax stepped back, panting, looking at me like I was a demon. "That's impossible. You didn't use any magic."

  "That is Fluid Dynamics," I said, shaking out my slightly aching thumb. "We don't use gears. The engine doesn't turn the legs. The engine turns a water pump. The pump forces liquid into cylinders at extreme pressure. A tiny amount of force, amplified by the fluid, can generate hundreds of tons of thrust. That is the blood of the machine."

  "But water won't work," I frowned, looking at a small leak in the leather hose. "Under extreme pressure, water cavitates. It boils. It rusts the cylinders. We need oil. Something incredibly viscous, heat-resistant, and incompressible."

  Rax wiped his brow, a strange look crossing his face. "Viscous... heat-resistant... If you don't mind the smell, the Alchemist Guild dumps something into the waste pits every day." "What is it?" Amelia asked, leaning in. "Troll-fat Sludge," Rax pinched his nose. "The leftover residue from their potions. Not even the feral dogs will touch it."

  Two hours later, I deeply regretted asking. The warehouse reeked of a stench that resembled dead rats mixed with raw sulfur. We wore masks soaked in vinegar, using thick cloth to filter four massive vats of dark red, gelatinous sludge. Amelia had actually run outside to throw up once. But I swallowed my nausea, pouring the revolting black sludge bucket by bucket into the emergency hydraulic reservoir we had welded together. Engineering was rarely glamorous.

  "Right knee joint assembly complete!" the old welder shouted from the scaffolding.

  We had connected the V8's output shaft to a high-pressure pump salvaged from an old mine. Several thick hoses made of multi-layered rubber ran like black intestines from the reservoir to the massive hydraulic cylinder on the Walker's right knee. This was our first localized test.

  "Start the engine!" I stood at the control console, pulling down my heavy goggles.

  Amelia stood by the distributor, channeling her mana. BOOM! CHUG-CHUG-CHUG— The V8 roared to life, spewing black smoke. The dust on the warehouse floor danced to the vibration.

  "Engaging the pump!" I yelled over the din, gripping the heavy metal lever that controlled the hydraulic valve. I could feel the terrifying vibration traveling up the handle. I took a deep breath and slowly pushed the lever forward.

  The high-pressure pump let out a piercing whine. The Troll-fat was being forced into the lines at thousands of pounds per square inch (PSI). CRACK... GROAN...

  The five-ton steel lower leg of the Siege Walker, rusted stiff for half a century, let out an agonizing screech of metal on metal. Flakes of rust rained down like a miniature storm. And then, driven by absolute physical violence, the massive steel limb slowly, steadily lifted.

  Ten degrees. Twenty degrees. Forty-five degrees. Like a waking giant, it kicked its metal foot into the air.

  "It moved! By the Gods, it actually moved!" The workers erupted into deafening cheers. Amelia was jumping up and down in excitement despite the engine noise.

  I stared at the pressure gauge. The needle was climbing insanely fast. 1000 PSI... 2000 PSI... 3000 PSI...

  "Something's wrong!" I roared. I saw the thick rubber hose connecting to the knee. It was bulging outward like a snake that had swallowed something far too large.

  "Get down! Cut the engine!" I screamed, abandoning the lever. I spun around, tackled Amelia who was standing too close to the line, and slammed us both to the concrete.

  BANG!!!

  It didn't sound like a balloon popping. It sounded like an artillery shell detonating. The thick rubber hose catastrophically failed under 3,500 PSI. Boiling hot, highly pressurized Troll-fat sludge acted like shotgun shrapnel. I felt like a sledgehammer had slammed into my back. The kinetic force threw me forward, sliding across the floor.

  Deprived of pressure, the hydraulic cylinder failed instantly. The five-ton steel leg, driven by gravity, crashed back down. BOOOOM! The concrete floor of the warehouse shattered into a spiderweb of craters, sending rock splinters flying.

  Dead silence followed, broken only by the sputtering, dying breaths of the V8 engine and the wet slapping sounds of the foul-smelling sludge raining down from the ceiling.

  "Julian!" Amelia scrambled up, her eyes wide with terror. I lay in a puddle of dirty water and black sludge, my ears ringing violently. My back felt like it was on fire. Nothing felt broken, but I was going to have massive bruising.

  I spat out a mouthful of foul-tasting oil and let Amelia help me stagger to my feet. I was drenched head-to-toe in Troll-fat. I looked like a swamp monster.

  Rax walked over, his face pale. He looked at the shredded remains of the rubber hose, then at the cratered floor. "It failed?" he muttered.

  I wiped a thick layer of black muck from my goggles. I looked at the broken hose. I wasn't angry. I wasn't despairing. I just felt the cold, hard reality of an engineer facing physical limits.

  "This is why the Mages look down on mechanics. This is why they spend millions on pure energy cores," I said, my voice raspy, laced with dark self-deprecation. "Magic has no mass. It has no friction. But matter has limits. The molecular structure of rubber cannot handle thousands of pounds of tearing force."

  "So we're done?" the old welder asked, looking defeated. "The Guard is outside, and our machine can't even lift its own leg."

  "We're not done." I peeled off my heavy, sludge-soaked jacket and dropped it with a wet thud. I walked over to the wreckage and picked up a piece of the torn rubber. "Fluid dynamics isn't wrong. The blood vessels are just too weak."

  I turned to Rax. "Get every weaver, chainmail maker, and wire-drawer you have. Take all the copper and steel wire we bought and draw it as thin as possible."

  "What are you doing?" Amelia asked, wiping a speck of oil from her cheek.

  I stared at the broken leg, picturing the heavy-duty hydraulic lines of earth-moving excavators. "Raw rubber is just flesh. We need to give the veins armor. We are going to weave a net of high-tensile steel wire directly into the rubber casing. We are building Wire-Braided Hydraulic Hoses."

  I took a deep breath of the sulfur-tainted air. The clock was ticking, and the threat of the Truth Mages was literally at our doorstep. "Take ten minutes to clean up. Then we go back to work."