The chimney passage was vertical. Not approximately vertical—not a steeply angled climb—but a true ninety-degree natural shaft, a volcanic chimney left by an ancient gas bubble in the basalt structure, rising straight up with smooth walls that offered nothing to grip and a width of barely two meters. Marcus looked up into it with a headlamp and estimated sixty meters to the top.
He turned to Talon. The raptor was studying the chimney walls with the systematic precision of its acoustic mapping, pulse directed upward along the stone surface, measuring wall texture and grip coefficient at multiple height intervals. When the assessment was complete, Talon moved to the base of the chimney and drove both sickled claws into the rock face at shoulder height.
The claws went into the basalt like climbing picks into ice. Marcus stared.
The sickled claw of Deinonychus antirrhopus was historically interpreted by paleontology as a hunting weapon—the killing tool used to grip and hold prey. But what Marcus watched now was a different application of the same anatomical feature: the backward-curved hook of the sickle, when driven into rock at the correct angle with the full force of the raptor's powerful hindlimb musculature, created a grip point that held under two hundred kilograms of downward tension without slipping.
Talon could free-climb a vertical basalt wall using its sickled claws as pitons. The raptor ascended six meters, found a solid ledge, and looked down at Marcus. Marcus looked at his own hands. His descent rig was in the supply pack left behind during their flight from the mercenaries.
What he had: three meters of survey cordage, a geological hammer, two steel core-sample extraction spikes. He drove the spikes into the wall. The hammer blows rang in the chimney like a bell.
Below, the magma surge reached the chamber entrance. Marcus went up. It was not graceful. It was hand-over-hand on improvised spikes, boots scraping for friction on smooth basalt, arms burning after the first ten meters, the geological hammer swinging from his wrist strap against the wall with each movement.
Talon descended to him twice—finding ledge points six meters above Marcus's position, looking down, waiting. The raptor couldn't lift a human being. But it could wait, and watch, and be something to climb toward.
At thirty-five meters, Marcus's left spike pulled from the wall. He dropped two meters before his right grip held, the survey cord snapping taut against its anchor point above with a tension that jarred his shoulder hard enough to white out his vision for a second. He hung there, breathing.
Forty meters below them, the floor of the chimney base glowed orange. Marcus reset the left spike, drove it with five hammer strikes, and kept climbing. At fifty-five meters, Talon reached him—the raptor pressed against the wall above him, one sickled claw gripping the chimney face, the other extended downward toward Marcus at shoulder level.
A grab point. Marcus gripped the offered claw with both hands—the feathers warm and rough under his palms—and Talon climbed. The raptor's hindlimb power was extraordinary: even hauling Marcus's added weight, Talon moved steadily upward for the final five meters until Marcus's hands found the rim of the chimney exit and he pulled himself through onto solid, cool rock.
He lay flat on his back for thirty seconds, breathing. Then he looked sideways, where Talon was sitting beside him with the composed dignity of a creature who found human climbing technique amusingly inefficient but had chosen to help anyway.
"Thank you," Marcus said.
The raptor clicked once.