The bell rang twice from the western approach and once from the Keystone chamber within the same four seconds.

For the length of those four seconds, the instrument room held two pieces of information that did not yet make sense together.

Two corridor signals would have been the entity’s escalation the garrison had been watching for since the third incursion, the dual-incursion scenario Darak’s analysis had flagged as the logical next step.

A corridor signal and a chamber signal together was not that scenario. It was something the analysis had not specifically described, and Aliyah understood in the same four seconds that not having specifically described it did not mean it was unrelated.

Oshrak’s response to the western corridor signal followed the now-standard no-pattern protocol. Yurakk from the western approach positions, highland warriors from whichever northern rotation slot happened to be active that hour, converging from different directions at different speeds with no fixed handoff.

The entity that came through the western wall was combat-profile, similar in scale to the second incursion’s entity though faster. The rotating contact formation absorbed it the way the formation had been built to absorb exactly this kind of thing.

The chamber signal was Aliyah’s own bell, rung by Vor’gath. He was the only other person in the third Keystone’s chamber, and the chamber had its own alert cord for exactly this kind of circumstance, even though it had never, until this moment, been used.

What had come through the chamber’s own wall, a small breach in the stone six feet from where Aliyah stood with her hands on the Keystone’s housing, was not combat-profile at all.

It was small, disoriented, the same approximate size and the same two-second window of confusion that the very first incursion’s probe had shown before Urrak put two wounds into it eleven weeks ago.

Aliyah could not leave the housing. The reinforcement sequence she was running was mid-cycle.

Stopping mid-cycle was not the same as not starting it. The binding’s structure did not return cleanly to its pre-reinforcement state if the reinforcement stopped partway through.

Vor’gath turned from his position below the housing toward the small disoriented thing six feet away, and did something Aliyah had never seen him do before.

The situation he was using it for had never occurred before, either.

The disruption ability he used on the patient entity, the one that made the entity’s spatial certainty waver for three-second windows at the chisel-and-grain distance of its work on the binding, he applied at point-blank range against something that was already disoriented and already small.

The effect at that range, against that target, was not a three-second hesitation.

The probe lost coherence in under ten seconds, faster than anything the garrison had previously dissolved. It had never had stability to begin with, and Vor’gath’s disruption had removed what little it was managing to hold onto.

For those ten seconds, Vor’gath’s attention was on the probe. Not on the patient entity’s pressure point in the third Keystone’s binding, which his disruption work normally interrupted on an irregular rhythm that Aliyah’s reinforcement timed itself around.

The patient entity, for those ten seconds, applied its pressure to the binding’s known vulnerability point with nothing interrupting it at all.

Aliyah felt it.

The choice in front of her was binary, and she had perhaps half a second to make it. Stop the reinforcement sequence entirely, which risked the binding deforming under a sudden loss of support mid-cycle, or continue without the disruption rhythm she had built her timing around for weeks.

Continuing meant the patient entity got ten seconds of clean, uninterrupted, optimal-angle pressure against active but undirected reinforcement.

She continued.

The third Keystone’s deviation reading, which had held in its narrow stability band for weeks, moved.

Not dramatically. A small uptick, the kind of movement that would have been within normal variance if the reading had been moving at all in recent weeks.

It had not been moving. Now it had. On any other day, a movement this small would not have been worth writing down at all, and today it was the only thing in the room anyone needed to see.

The probe dissolved. Vor’gath’s attention returned to the binding within the same second.

The patient entity’s pressure, no longer unopposed, settled back into the angle Vor’gath’s resumed disruption made it work for.

The deviation reading did not climb further. It also did not return to where it had been.

Prenn, at the sixth Keystone’s dedicated station, reported no change throughout the entire sequence.

Whatever this had been, it had not been aimed at the sixth Keystone. Prenn’s standing assignment there, made in the days after the third incursion so the sixth Keystone would never again be the unwatched gap during an active engagement, had functioned exactly as intended.

This time, the sixth Keystone was simply not where the attention was going.

The western corridor fight ended at the fourteenth minute. Oshrak counted four down, all functional, none critical, the formation’s now-familiar outcome for a combat-profile entity of that scale.

Aliyah finished the reinforcement cycle eleven minutes after the probe dissolved, because the cycle had a natural endpoint and ending it early would have created its own problem.

When she finally stepped back from the housing, the third Keystone’s reading sat a fraction above where it had sat for weeks. A small permanent increase, against a binding that had not given ground since the emergency reinforcement weeks earlier.

She looked at the small dark scar on the chamber wall where the probe had come through, and at Vor’gath, who was still kneeling at the housing’s base, visibly more depleted than the disruption rhythm alone usually left him.

"It was not trying to breach the chamber," she said. "The breach itself was the small thing. The probe was the weapon, and the weapon was your attention, not the binding directly."

"I know," Vor’gath said. He did not get up immediately. "A larger probe would have been easier to fight, and would have done less."