Rung seven chimed at a T-junction where the air moved wrong. A crosswind ran through the stone like a draft that had learned to lie. It tugged on Hollow's ribs and made him correct mid-flight, wings canting, skull ticking to keep balance.
"Vent failure," I said. "Backflow from the core."
"Leak?" Cael asked, eyes already measuring corners.
"Or someone turned the baffle," I said. "We're being steered."
He looked down the right branch where old ward stenciling pointed us like polite arrows, nearly worn away by boots. The left path wore fresh chalk: two lines and a circle, strokes clean and sure. Dorian's field marks—quiet handwriting that meant, this way is live.
"Right's original," I said. "Left is current."
"Left," Cael said.
