“I can't,” she said. She had backed into the corner and held the knife up before her, shaking as if she did not know which way to aim the blade: outward, or inward. “What have we done?”

“Found a God,” Ramus said, but his voice sounded distant and insignificant now, and nothing he could say would match the grandness of this moment. So he fell silent as he worked the knife upward, widening the cut and trying to see inside. It was too dark, and the air emerging was joined by a waft of steam that scorched his face, dried his eyes. He winced and stepped back. He still held the knife, aimed at another part of the sac, ready to start another cut . . . but it was not needed.

The sac shivered all across its surface. Dust shimmered into the damp air. The pipes protruding from the sac shook, and the junctions where they met the roof and walls cracked and poured dust and grit. Ramus saw for the first time that they were partly transparent, and something seemed to boil and roll within, like clouds driven into a frenzy by a terrible storm.

Shadows reached into the pipes. These shapes had defined edges, sharp against the tumult, and they bent and pressed against the fleshy sides, stretching them to the point of breaking.

The Sentinels screeched, Nomi shouted something, but Ramus did not understand. Language seemed superfluous against something so powerful and elemental.

The first pipe broke. Something gushed from it, a heavy fluid that barely splashed when it touched the ground. Gases rose and twisted in the air, forming shapes that seemed to move of their own volition. A black, shiny thing protruded from the rent in the pipe. Its sharp end opened like a giant claw. It clicked shut again, and in that brief, violent sound Ramus heard laughter and weeping.

The Sentinels had fallen silent.

Another pipe ruptured, and another, and the chamber floor was covered with the slick, hot fluid. Vapors danced before Ramus's eyes and within, seemingly working their way into his mind and flirting with memories, toying with identity. He felt threatened and courted, and when he raised the knife it burned his palm and fell into the fluid at his feet.

The things withdrew back into the sac, and for a while it was silent and motionless. The shapes trembling in the air dispersed into shapeless drifts, waving here and there with the effects of their combined exhalations.

I'm still breathing, Ramus thought. He remembered Ten, their journey south and the climb, and history flooded back in, returning his self. The presence was no longer in his mind with hands wrapped around his illness, ready to squeeze and coerce.

He looked away from the sac for a beat and Nomi was looking at him. She no longer seemed shocked, terrified or surprised. Her eyes now were full of blame.

“They've gone,” he said, nodding up at the roof.