The second layer was darker, but not because the lights failed.
It was darker because the walls here absorbed light instead of reflecting it.
Material change. Purposeful.
Yara tested it with her penlight: the beam thinned, swallowed at the edges, as if the wall wanted contrast rather than illumination.
"Photonic dampening," she said.
Rin looked at her. "…You're the first surface dweller I've heard use that term correctly."
"I don't use terms incorrectly."
They moved deeper.
The corridor ahead wasn't long, but it lacked the comfortable symmetry of the first layer. The floor sloped slightly left, the ceiling angled right, and the dimensions adjusted almost imperceptibly with every few meters.
Like walking through a structure that corrected itself around them.
"This level wasn't designed for passage," Rin said.
"No," Yara replied, "it was designed for calibration."
Before Rin could question her, the corridor emitted a low hum—different from the resonance above. This one was rotational, like gears turning behind a sealed wall.
Yara raised her hand.
"Stop."
She didn't sound alarmed. She sounded analytical.
Rin halted silently.
A section of the floor ahead shimmered. Not visually—physically. A thin ripple passed through the material like pressure equalizing.
Rin's voice was low. "Shift zone."
Yara nodded. "A displacement panel."
"You shouldn't know that."
"You shouldn't assume what I know."
Rin's mouth tightened, but not in annoyance—more in reassessment.
Yara crouched near the edge of the shimmer, holding her penlight close without crossing the boundary. A thin vibration passed through the air, brushing her knuckles.
"Localized spatial drift," she said. "Short-range, nondirectional. It resets every cycle."
Rin watched her. "Cycle time?"
"Unclear." Yara checked her sensor. "But the pressure drop suggests thirty seconds."
Rin blinked once—the closest she showed to surprise.
"You estimated that from airflow?"
"I confirmed it from airflow."
The ripple passed again, stronger this time.
A small object—dust, maybe a fragment from the upper collapse—rolled forward on the floor, hit the panel, and vanished.
Not destroyed. Just displaced.
"Where does it go?" Yara asked.
Rin hesitated. "…Another part of the layer. Not harmful. Just… unpredictable."
Yara stood.
"We're crossing it."
Rin moved in front of her. "No. You don't have mapping."
"You do."
Rin's eyes narrowed. "You're assuming I'll lead you."
"I'm assuming you came here for more than warnings."
Silence.
Then Rin stepped aside—not submission, but acknowledgment.
"The moment the panel stabilizes," Rin said, "we cross. Don't stop in the middle."
"I don't stop anywhere unnecessarily."
The shimmer softened—its surface tension flattening.
Yara was already moving.
She didn't wait for Rin.
She walked with measured, confident strides across the panel as the air oscillated around her. Her boots hit the far side without hesitation.
Rin arrived a step after her.
The corridor straightened ahead—geometry normalizing again.
Yara spoke first.
"That wasn't a defense system."
"No," Rin agreed. "A filter."
"For what?"
"For alignment. These layers weren't designed to block intruders. They were designed to recognize movement signatures."
Yara absorbed that.
"So this place is reading us."
"It's reading you more than me."
Yara didn't react outwardly.
But inwardly, pieces moved.
They continued forward until the corridor opened into a chamber smaller than the previous one—more functional, less architectural. The walls were lined with panel recesses, each holding an object shaped like a flattened sphere, embedded flush with the material.
Only one of them was active.
A soft blue pulse glowed within it, steady and calm.
Yara approached.
"What function?"
Rin stepped beside her. "It's a regulator. This layer's central one."
"Temperature?"
"No."
"Pressure?"
"No."
Yara looked at her.
"Rin."
Rin exhaled.
"It regulates movement permissions," she said. "Every level of the Veins had a different threshold. Spatial inconsistencies. Old architecture isn't stable."
Yara examined the pulse.
"And this is granting permission?"
"It's granting recognition."
Yara lifted her eyes. "Of what?"
Rin held her gaze with rare directness.
"Of you."
The pulse brightened, responding to Yara's proximity. Not violently. Not alarmingly.
Just… with certainty.
"Why me?" Yara asked.
Rin shook her head.
"I don't know. But I know what comes next."
"Tell me."
Rin pointed to the far wall—where a narrow door was materializing out of the surface, its outline forming with geometric precision.
"That," Rin said, "is the entry to the third layer."
"And its function?"
Rin answered without hesitation this time.
"It's where the Veins begin showing you why they exist."
Yara didn't pause.
"Then we're going."
Rin stepped beside her, matching her pace.
"You're aware the third layer reacts more aggressively," Rin said.
"Yes."
"And it has no recorded safe path."
"Yes."
"You're not concerned."
"No."
Rin allowed a very small exhale—almost a laugh, but sharper.
"You're more dangerous than the Veins," she said.
Yara placed a hand near the forming door, observing the temperature, the material shift, the alignment.
"Everything becomes less dangerous," Yara said, "once you understand how it thinks."
The door slid open with quiet acceptance.
Yara stepped through first.
Rin followed.
The door sealed behind them—soft, final, certain.