The upkeep vat was a box-shaped trough of riveted boilerplate, sunk three feet into the dark rock floor of the ancient forge shop.
It was filled with dark, thick, sticky stone oil that smelled of sulfur, lamp-wax, and cold iron. Underwater to his waist in the black bath sat Unit Ren, his iron boots resting on the settled mud at the bottom of the vat, his torso braced against an overhead timber chain-hoist. His left arm—the massive, mangled assembly of cut pistons and crumpled hard dark metal plate—lay across an iron work-table beside the vat, still connected to his shoulder by three fraying copper tracking data cables.
Around the vat, the coke forge burned with white, roaring heat, lighting up the cave in dancing crimson light.
Ren Vale stood over the table. His lambskin apron was tied back, his sleeves rolled above his elbows. Between his thumb and forefinger, he held his ivory mammoth bone awl. With his left hand, he held a glowing copper soldering iron pulled fresh from the coke coals.
“The high-pressure return valve is fractured along the thread line,” Ren said, his voice flat as he leaned over the iron gearwork. “If I heat the copper line too quickly, the silver wire will melt before the solder seats in the groove.”
