The opening was wider than Ayla had prepared for.

She had walked corridors of stone for two days. She had walked vessels and chambers and pools full of things that had wanted to eat her.

None of it had prepared her for this.

The corridor emptied into a cavern shaped like the inside of a throat. The walls curved outward and rose into a vault she could not see the top of, lost in the warm dark.

The floor sloped downward into darkness. At the far end, perhaps two hundred meters away, the chamber narrowed again into a ringed aperture.

The mouth.

Ayla took one step forward and stopped at the threshold.

"It is alive."

"Everything down here is alive," Kenji said behind her.

"Not like this."

She was right, and she knew she was right. The tunnels they had crossed had been the body’s vessels.

The slimes had been waste. The spider nests had been parasites. This chamber was different. The walls flexed. The ceiling exhaled.

The aperture at the far end was the only part of the host still doing what the host had been built to do, and what the host had been built to do was eat.

"Stay close to the wall," Kenji said. "The middle of the chamber is where it pulls things in."

He stepped onto the slope. The stone gave slightly under his boot.

Ayla followed.

They moved along the right-hand wall, hugging the curve. The slope was steeper than it had looked from the threshold.

Kenji kept one hand against the stone for balance. Ayla did the same. Halfway down, Kenji paused.

"Wait." 𝗳𝚛𝗲𝕖𝕨𝕖𝗯𝚗𝚘𝕧𝕖𝗹.𝗰𝗼𝕞

"What."

"It is breathing faster."

Ayla cocked her head.

The pulse from the aperture had been slow and measured a minute ago. Now it was quicker.

Each breath pulled a thin draft of air down the chamber and into the mouth. The draft had begun to tug at the edges of her shirt.

"It knows we are here," she said.

The aperture pulsed again. The draft sharpened. A loose piece of stone on the slope slid past Kenji’s boot and tumbled down toward the ring of plates at the far end.

The stone disappeared into the dark beyond the ring without a sound.

Kenji’s voice tightened.

"We move faster."

Ayla glanced back over her shoulder. The corridor they had come from was still dry.

They moved.

The slope continued for another hundred meters. The pull of the aperture grew stronger as they descended. The draft turned into a current. Kenji’s coat lifted at the hem.

Ayla’s hair began to drift forward around her shoulders, as if she were standing at the edge of a cliff in a steady wind.

"Kenji."

"I see it."

The teeth at the far end of the chamber were not teeth. Ayla had thought they were teeth at first. They were not.

They were a ring of curved bone plates, set in concentric circles, each circle rotating slightly out of phase with the one behind it.

The plates ground against one another with a dry, papery sound. They had been grinding for so long that the grooves between them were polished smooth.

"There is no opening."

"There is."

"Where."

"Above the third ring. There is a gap in the bone. It only opens when the host swallows."

"The host swallows slowly, be prepared," Kenji warned.

Ayla looked up. The gap was visible if you knew where to look. A thin dark line above the third ring of plates.

The dark line was perhaps a meter wide. It was perhaps three meters tall. It would close again in seconds when the host’s slow pulse reset.

"How long do we have."

"Maybe twenty seconds. Maybe ten."

The chamber pulsed again. Closer to fifteen now. The draft had become a wind. A strand of her silver hair lifted and pulled forward toward the aperture.

"Kenji."

"I know."

"You have to go first."

He turned to look at her.

"Why."

"Because if I go first and you do not make it, I cannot pull you through. If you go first and I do not make it, I will make it anyway."

He did not have time to argue with the logic. He nodded once.

The wind pulled harder.

He ran.

Ayla watched him go.

The slope was steep. The stone was soft. He slipped twice and caught himself on his hands once, palms scraping the warm flesh of the floor.

The aperture was forty meters away. Thirty. Twenty. The gap above the third ring was visible now, a thin band of darker dark in a wall of pale bone, and the gap was closing.

She could have run with him. She had chosen not to.

He needed the clean window. If she crowded him at the threshold, the gap might catch one of them and let the other through, and the wrong one would die.

She had calculated the angle and decided that her body could handle being late. His could not.

The gap was three meters tall.

Then two.

Then one.

Kenji jumped.

He cleared the third ring and slid through the gap on his side.

The bone closed against his shoulder hard enough to bruise. Ayla saw him tumble through and drop into open air on the other side.

The plates ground shut behind him.

The chamber went quiet.

Ayla stood at the center of the slope. The wind had died with the closing of the aperture.

The host’s slow swallow had completed. The next swallow would not arrive for several minutes.

She could hear Kenji on the other side of the bone wall.

"Ayla."

His voice cracked. The crack was new. She had not heard it before in any of his voices.

"Ayla."

She tilted her head.

He thought she had not made it.

She considered, for a brief and amused second, letting him think it for a little longer. The thought passed. There would be time for that kind of cruelty later.

She walked down the rest of the slope at her own pace.

The bone wall in front of her was perhaps two meters thick. She had not measured the exact thickness.

She did not need to. She placed her palm against the wall and let Acid Synthesis bloom under her fingers.

A thin line opened in the surface.

She slipped her hand through. Then her arm. Then her shoulder. Then the rest of her, sliding through the cut. The cut sealed behind her without leaving a mark.

She landed on her feet in front of Kenji.

He stared at her.

"Sorry," she said. "The wind was strong."

"You cut through bone."

"I have Acid Synthesis now."

He kept staring.

She brushed her hair back from her face and looked past him at what lay ahead.

The chamber on this side of the wall was vast. The light was a dim, organic red, pulsing in time with something larger and slower than the mouth.

The walls curved upward into a dome that had to be a kilometer across. The floor was not stone. It was tissue. Ridged. Folded. Wet.

In the center of the chamber, suspended above the floor by a lattice of grey-white cords, sat a mass the size of a small mountain.

Pale. Folded. Pulsing.

The brain of the host.

Below it, at the edge of the lattice, something moved.

Smaller than the brain. Far smaller. Roughly the size of a man, but only roughly.

Ayla’s expression sharpened.

"What is that."

His mouth had gone dry.

"That is what killed me every time."

The thing turned its head.

It saw them.