Li Xiao Bai did not rush the boundary.
Rushing was for people who still believed the universe rewarded bravery.
He drifted along the system's perimeter in a slow arc, careful to keep outside the range where his earlier probe had been erased. He moved like dead debris, letting inertia do most of the work and correcting only when the angle slipped. Every adjustment was counted. Every activation was weighed against what it would cost later.
The space here felt arranged.
Not gentle. Not welcoming.
Arranged.
Farther out, the void had been raw. Foreign residue scraped at flesh and tools with blind persistence, like sand in a wound that never healed. Here, the pressure had intent. Dao marks overlapped and interlocked in a continuous shell that wrapped the whole system in an invisible sphere. You could not see it, but you could feel how space stopped behaving normally once you drifted too close.
A boundary that selected.
He did not decide what it was yet. Prison, filter, laboratory wall. Names were cheap. Certainty was not.
He circled for what could have been days. Without a horizon, time became endurance. The sun remained his only honest reference, a fixed blaze that let him keep orientation while everything else lied. The planets were anchors in a map he rebuilt and revised, not because he trusted what he saw, but because patterns still existed even when light arrived late.
Light delay was a cruel joke. A world could look close and still be months away in real distance. He did not rely on sight alone.
He relied on gradients.
The shell was not uniform. In some regions the pressure was thicker, sharper, more rigid, like rules written twice for emphasis. In other regions it softened by a fraction, not enough to call a gap, but enough to suggest overlap that was stretched thin.
Edges.
If it had been made, it had weak points. Even the cleanest formation carried a flaw because everything that defended also had to operate, and operation always meant timing.
He started with matter.
Not Gu constructs. Not anything that would announce cultivation.
He took small pebbles of ordinary ice and stone and flicked them forward from safe angles.
They drifted across the outer pressure.
Nothing dramatic happened.
They did not vanish. They did not flare. They kept moving, slipping into the region where his earlier probe had been denied.
Li Xiao Bai watched without widening his senses. He let normal sight do most of the work and used only the faintest readings that stopped short of the lethal band. He wanted to observe without touching.
Deeper inside, some pebbles slowed as if space thickened. Others curved in tiny arcs, not like gravity, but like correction. Their outlines blurred once the shell began bending light, turning clear silhouettes into sunlit haze.
Still, the pebbles remained.
Matter could pass.
Function could not.
That was the pattern he needed to confirm.
He sent another pebble, this time tagged with the weakest possible information imprint. A scent, not a leash. Just enough to track it through his own perception without throwing a net into hostile water.
The pebble crossed the outer pressure.
The imprint survived.
Then, the instant the pebble entered the range where structured methods failed, the imprint snapped.
Not slowly.
Not with resistance.
It severed as if the concept of connection itself had been refused permission.
The pebble continued inward, physically present, drifting as before. Only the law that made it traceable had been cut away.
Li Xiao Bai stared at the empty point where the link had been.
So the shell was not killing Gu because Gu were insects.
It was denying the rules that made them function.
Information. Connection. Dao marks shaped into meaning.
A barrier that defended the system by refusing foreign frameworks permission to operate.
He let the conclusion settle without fear. Fear was heat, and heat showed.
If he crossed, his methods might fail inside his aperture the same way. Maybe they would die outright. Maybe they would survive but become useless, their inner logic stripped until only husks remained.
If that happened, he would not be an immortal here.
He would be a wounded man with a soul held together by something he did not own.
He did not retreat.
He continued his arc.
The void had already forced him into worse positions. You did not survive a year out there by stepping back every time the next move looked dangerous. Every move was dangerous. The only difference was whether the danger could be understood.
As he drifted, he noticed something else.
The region near the shell was clean.
Clean in a way that felt maintained.
Out in the deeper dark, debris existed everywhere. Dust, fragments, slow leftovers of collisions. Here, drifting objects were rarer. Not absent, but reduced, as if anything that wandered too close was removed before it could accumulate.
That did not suggest a broom.
It suggested a current.
A processing flow that broke down what entered and carried it away.
He needed proof.
He opened his aperture a sliver and produced a small creature he had preserved for experiments. Not a Gu insect. Not a refined tool. A mundane animal that had once lived inside his own controlled environment.
He released it into open void.
It tumbled in vacuum, limbs jerking, mouth opening in silent panic. Within seconds its body stiffened, dried, whitened. The void did what it always did. It killed.
No answer there.
So he changed the variable.
He nudged the dead body toward the shell with a gentle push.
It crossed the outer pressure.
Nothing rejected it.
Then it entered the region where the shell's rhythm pulsed like waves against an unseen shore.
The corpse changed.
Not violently.
Wrongly.
Brittle flesh softened as if rewound. The whitened surface darkened for a heartbeat, almost convincing, almost alive in silhouette.
Then it crumpled into dust.
Dust that did not scatter.
Dust that spiraled.
An invisible flow caught it and carried it along the shell's curve, circling the system like a river around a fortress wall.
Li Xiao Bai's remaining eye narrowed.
So it was not just a filter.
It processed.
Anything that drifted too close was broken down and swept into circulation. That was why the region stayed clean. That was why approaching debris was rare. It was not absence. It was maintenance.
A mechanism that behaved like a predator without needing hunger or thought.
Mechanisms still had habits.
Habits could be exploited.
He followed the direction of that unseen current from a safe distance, never chasing too close, watching how fine fragments moved when the pulse hit. Slowly, an image formed in his mind.
The shell had layers.
An outer layer that distorted light and corrected motion.
An inner layer that denied structured function.
A pulsing region that processed what survived and fed it into a circulating flow.
If there were seams, they would be where those layers overlapped imperfectly, where timing slipped, where a pulse arrived late.
He waited for stutters.
Most pulses were clean.
Then one arrived a fraction late.
The pressure dipped, small enough to miss if you were not looking for it, then recovered as if embarrassed.
A flaw.
He did not rush it. He tested.
A pebble, unmarked, went in along that arc. It bent differently for a blink, wobbling as the current hesitated, unsure how to take it, then the next pulse arrived and the pebble was swallowed into the flow.
Li Xiao Bai replayed the moment in his mind until it became a measurement.
The wobble lasted less than a breath.
Not enough for a large method.
Enough for a simple vector shift.
Enough to slip past one layer before the next one corrected.
He backed away to safer distance and sat in empty space with no chair, no ground, no sky. Rest, for him, was only review. He went through what remained: the Gu still alive, the essence still stored, the methods that did not require wide perception, the tricks that could be done with minimal noise.
He counted his tools the way a butcher counted knives.
Then he built the next step.
He would not send Gu first.
He would not send anything marked.
He would send mass.
Something disposable, large enough to strain the processing flow for a fraction longer, heavy enough to force the shell to spend effort correcting it.
A battering ram.
He drew a rough block of inert debris from storage, dense ice bound with stone, and held it with his remaining hand. He insulated his skin with the thinnest layer of essence he could afford, feeling the cold through it like a warning.
He did not throw immediately.
He waited for the rhythm.
One pulse.
Two.
Three.
The stutter came.
He moved.
He pushed the block forward with a careful burst, sending it toward the flaw, not too fast to draw attention, not too slow to be pointless.
It crossed the outer pressure and slowed.
Space corrected its path.
It entered the pulsing region and the current tried to take it. The mass resisted, forcing strain into the flow. The pulse arrived late again and the current kinked.
Li Xiao Bai acted on the kink.
No grand movement.
No loud method.
A restrained burst that shifted his trajectory sideways and inward, aiming for the disturbance window.
The pressure thickened around him at once.
His aperture tightened as if an unseen hand had closed around it.
Concealment flickered.
He forced it steady with discipline, not force, keeping everything quiet enough to be mistaken for debris caught in a stream.
Then he felt it.
Not an attack.
A question.
A silent evaluation pressed against the concept of his existence, as if something inside the shell had noticed an anomaly and reached out to judge whether it belonged.
Li Xiao Bai shut down every unnecessary motion. He sealed his essence further. He made himself as close to dead as possible while still moving.
The pressure lingered.
Then withdrew, as if disappointed.
Ahead, the block began to crumble at last, caught and processed. Dust spiraled away, pulled into the circulating flow. The disturbance window narrowed.
Li Xiao Bai was still inside the outer correction layer.
The inner denial layer waited ahead like a blade that did not cut flesh, but function.
If he hesitated, the current would catch him and sweep him away.
If he pushed through, the shell would decide what parts of him were permitted to remain meaningful.
He chose forward.
The moment he entered the thicker band, his aperture shuddered.
Somewhere inside, one of his Gu trembled.
Then another.
A cold sensation slid across his awareness, not pain, not fear, but judgment. Something was being measured against a rule that did not belong to him.
Li Xiao Bai clenched his jaw and kept drifting inward.
The sun burned ahead, indifferent.
Behind him, the last resistance of the battering ram dissolved into dust and vanished into the circulating flow.
The shell closed back into rhythm.
And the system's boundary began to decide what it would allow inside.