The air inside the main vaulted conduit of the Old Hill was suffocatingly hot, thick with the oily reek of heated mineral lubricant and sulfur smoke.
Jon Hale stepped along the narrow masonry catwalk, his boots slipping on condensation that dripped constantly from the curving granite vaulting above. The temperature had risen past eighty degrees in the first hundred paces, and with every step into the mountain, the heat thickened like wool soaked in boiling grease. The high-pitched vibration of the waking Crown Furnace buzzed through the stones—a sound so intense that it made Jon’s teeth ache and set the brass buckle of his leather coat humming against his ribs.
Ahead of him, Sir Cael Ardent moved in a low, disciplined crouch, his raw-hide kite shield raised to cover his head and torso, his notched broadsword held at the low guard. The former Returner moved with silent, feline grace, his boots making no sound in the shallow river wash that ran along the central flume. Even without the supernatural buffs of the Hearth Nail, Cael’s combat instincts were formidable; he checked every blind archway, tested the footing before committing his weight, and kept his shoulders square to the threat.
“Watch the joints,” Alden Bram whispered from behind Jon, his voice a gravelly rasp in the close, humid dark. “Ors’s sappers were in a hurry, but they knew where to drill. Look at that keystone.”
