Burrow Miner had chased the legend his whole life, and today it was killing him. Deep in the volcano's shaft, he swung his pickaxe at black rock that glowed orange at the edges. The molten vein slept below him, the richest ore any miner ever dreamed of. His lamp lit the tunnel. His pointed nose dripped sweat. Each strike brought him closer to the volcano's burning heart. Then the heat changed. It stopped feeling warm and started feeling like a slap. Burrow gasped and tasted rotten eggs. Fumes seeped from a fresh crack in the wall. His head spun. His lamp swam in front of his eyes. He knew this feeling. Miners who felt it too long never climbed back out. He backed up the shaft, coughing hard. He could not reach the molten vein like this. The deeper he dug, the hotter and more poisoned the air became. His pickaxe alone would not carry him to the core. He needed cool air pushed down where no air wanted to go. At the mine's snowy mouth, a young man stood beside a towering machine. Caleb Cinderspark II worked in his father's steam workshop, and he shared his father's stubborn genius. He wore winter armor he had forged himself. His serious face studied the drilling rig, a huge frost-crusted tower of pipes and vents. He wanted rare ore too, for the greatest blades in the world. That made him useful to Burrow, and dangerous. "That machine breathes," Burrow rasped, pointing. "It pulls cold from the snow. Turn its vents down my shaft, and I live long enough to reach the vein." Caleb crossed his arms. "My rig, my terms. You strike the molten ore, I get first pick of it." Burrow hated bargains. He hated sharing more. But he coughed again, and his choice was made. "Half," he said. "And you keep it running while I dig." "Done." They hauled the frost driller to the shaft mouth. Caleb aimed its long vent pipes into the dark. Steam hissed. Gears bit. Then a cold wind roared down into the volcano, thick with the smell of snow. Burrow climbed back into the heat. This time the air fought the fumes. He breathed. He swung. Hours later his pickaxe cracked through the last black wall. Molten ore spilled out, gold and red and alive. Burrow had reached the legendary vein at last. But the cold wind and the molten heat met in that narrow space. The rock groaned. A deep crack split the tunnel above his head. Somewhere higher up, the driller's roar turned to a shriek of tearing metal. Caleb's voice echoed down, sharp with alarm. "Burrow! The rig's coming apart! Get out!" Burrow stared at the treasure he had chased his whole life. Then he stared at the widening crack. He had the vein. Now the mountain wanted to bury him with it.

The crack widened above Burrow's head. Fumes poured through it, thick and sour. His lamp lit a haze that stung his eyes. The molten vein glowed at his feet, gold and red, the treasure of his whole life. Up top, the frost driller screamed and died. The cold wind stopped. Heat rushed back into the shaft like a closing fist. Burrow gripped his pickaxe. He did not climb out. He swung again. "Burrow! It's dead! The rig's finished!" Caleb Cinderspark II's voice fell down the shaft, hard and flat. Boots scraped on rock. The young blacksmith climbed down into the smoke, one hand over his mouth. His winter armor was scorched at the shoulder. He had built the machine that saved Burrow's lungs. Now he stood in the ruin of their deal, coughing, furious. "You promised me half. There is no half if you die down here. Drop the pick." Burrow kept chipping loose ore. His chest burned. Each breath tasted like rotten eggs. "Almost," he rasped. "Almost mine." "It was ours." Caleb grabbed Burrow's arm. "The vents are slag. My father's rig, gone. I get nothing, and you'll get a grave." Burrow shoved him off and struck the vein once more. A chunk of molten ore broke free. He raked it into his pouch with the pick's edge. Then the ceiling groaned. A slab dropped where his head had been. Rock and heat filled the gap. The path out of the hollow cave back to civilization was closed. The two were stuck in here with rising fumes and temperatures and oxygen was lowering.