Yaz has a barrel chest and a compact, powerful stance, as if even at rest he is braced against a furnace door. White, branching burn scars web his forearms and collarbones, while his weathered skin carries a permanent sheen of heat and fine iron dust. The adamantine brace on his right forearm is a dense lattice of pistons, rivets, and soot-dark joints; it clicks softly when he flexes. He walks with a measured heel-to-toe tread that makes the floor seem to answer him. Unexpectedly for a foundry organizer, he keeps a tiny, carefully tended pot of mint on his office windowsill, and rubs a leaf between his fingers before difficult meetings.

Yaz is patient with frightened workers and hard-edged with officials who disguise danger in polished language. He can be generous with credit yet stubborn about surrendering control, and his protective instincts sometimes become a refusal to let anyone else take a risk. In a crisis he turns brisk and decisive; when the danger passes, guilt and second-guessing catch up with him.

Yaz began as a furnace tender in the lowest galleries of the Great Caldera and Ignis Reach. During a preventable vent failure, he heard trapped workers hammering on the other side of a buckling bulkhead while supervisors ordered the line kept running. He disobeyed, hauled the emergency gate open with a chain hoist, and survived the blowout with his right forearm crushed. The brace built afterward saved his livelihood, but the names of those he could not reach still shape every decision he makes. Years later, he helped organize a stoppage at Slag Ford that forced the foundries to inspect unstable routes before restarting. He now serves as chief organizer and delegate of the Cleared-Vent Compact, arranging aid, evacuation routes, and compensation while negotiating with employers who would rather call a dangerous delay sabotage. His closest working ally is Tavi, a route examiner who challenges his instinct to shoulder every risk himself. His former supervisor, Ruk, now advises a foundry council and insists that production delays will cost lives too. Yaz keeps meeting both of them, because the crews need leverage more than they need a clean feud.