The pale blue bead of flame inside Paxa Sel’s safety lamp guttered and shivered like a dying ember. The golden animal fat light that had lit up their descent down three hundred paces of dark stone had collapsed into a ghostly halo no larger than a pea. They were surrounded by a faint, purplish ring of uncombusted gas.
Yseld Arken didn’t need to be told what the blue bead meant. With a gut, trained reaction, the former mountain scout reached to her belt, ripped the white linen STOP paddle from its loop. Then it held it high above her head while pressing her back flat against the cold baked flint-rock wall.
“Choke-damp,” Paxa said. Her voice dropped to a low, measured whisper that carried no trace of panic, only the total clarity of an experienced physician facing a lethal contagion. “Heavy carbonic acid gas, mixed with cold air and stale moisture. It has settled into this lower drift like oil on water. Step back two paces, Kezra. Don’t inhale deeply.”
Kezra took two slow, disciplined steps backward onto the stairway landing, her boots careful on the damp stone. She felt the heavy, choking pressure of the air against her chest. A subtle, cloying weight that made her lungs work twice as hard to draw a breath. Meanwhile, a bitter, soda-water taste coated the back of her tongue.
