Night over Cadia was not dark so much as disciplined. Searchlights quartered the sky in measured arcs; bastions breathed in a slow rhythm of ready-fire-ready; the pylons threw long, knife-straight shadows that did not waver even when the wind remembered to exist. The Eye of Terror sulked beyond the horizon, a bruise learning to smile.
Aurelius walked the gravel spine between Pylon Seven and its attendant bastion with Seraphine one pace left and half a pace back—close enough that their auras brushed like blades in a tight scabbard. Magos Belth rattled along beside them on crabbed augmetics, a cowl of stamped prayers clacking against his gorget. Tech-adepts trailed with sensor-tithes, auspexes, incense-swingers, and the sort of courage that had to be recited in machine-litanies to continue existing.
"Residual interference persists," Belth rasped, vox-grille hissing. "Auspex failures along sub-stratum channels. Machine-spirits… uneasy."
"Not warp?" Aurelius asked.
"Not… precisely." The Magos's mechadendrites made a doubtful noise. "A resonance. Geometry that dislikes being mapped."
Seraphine slowed, head tilting. Her null-field rose a hair. The air went clean, then cleaner, as if a second silence had been laid atop the first. "Here," she signed, two fingers describing a shallow V toward the pylon's plinth. Hollow.
Aurelius let Observation pulse downward in a thin, precise cone. For half a heartbeat the strata drew itself like a charcoal etching in his mind—layers of rock, a culvert abandoned by honest water, and beneath it a void: a perfect chamber cut by someone who didn't care for ornament because it had discovered contempt for it. The walls returned nothing. Not emptiness—refusal.
He set his gauntlet to the pylon's base. The black stone did not feel like stone. It felt like the absence of question.
"Access?" he said.
Belth clacked. "A maintenance conduit runs under the west spur. Cut during previous survey and—ah—subsequently forgotten for everyone's safety."
"Remember it," Aurelius said. "We're going in."
The conduit had been a drain in saner ages. Now it was a throat. Sump-lamps threw cones of pallid light; sacred oils made the metal smell like old church and new weapon. Two Cadian sapper-squads went first, Havel-quiet despite never having met Havel: boots placed where boards would not confess, breath held like a virtue. Aurelius followed. Seraphine moved as subtraction. Belth brought up the midline, whispering to reluctant hinges like a patient uncle to children who had been told too many stories about the dark.
Fifty meters down, the conduit bent and became less conduit and more… decision. The seams between human work and the older cut did not meet; they ignored each other, each proud of its lineage. Seraphine's null-field found the lip and hummed—not audibly, but in the bones, a pressure that said this is where the noise begins.
The first of the constructs came when the last of the men had decided they would prefer not to think about their hearts.
It was small as a hand and fell like guilt from the ceiling, a spined beetle of impossible angles. Its surface flickered between dullness and a oily shine that made eyes lose their footing. It landed on a sapper's pauldron and tried to make a home in his collarbone.
Aurelius's spear snapped sideways and pinned it to the wall before anyone had time to misname it. The bug writhed, little claws scratching patterns that aspired to be letters and remained insult. Seraphine stepped nearer and its movements slowed, then stopped, as if remembering inertia is not a law but a treaty.
"Xenos?" hissed a sapper.
"Foreign," Aurelius said. He wrenched the spear free. The thing left a smear behind that wasn't blood and didn't wish to be described.
More dropped. Not a swarm—a test. They scuttled toward the null, then away, then toward the biggest source of intention in the corridor. Aurelius adjusted: Observation pulsed in tight bursts along the ceiling's lines, mapping the next falls to hand-widths, not meters. He struck with the spear's butt as often as the blade, crushing, stunning, redirecting mid-air. The sappers learned his rhythm the way men learn to set nails where a master points; a dozen creatures died in silence because noise would have been disrespectful.
"Back hatch," a corporal voxed, trying to keep awe out of his mouth. "Opens to the chamber."
"Open it," Aurelius said.
They did. The door was not a door. It was a piece of human sheet-steel welded to a larger truth and pretending it mattered. It came away like etiquette when someone important is tired.
The chamber beyond was a geometry lesson written by a god that didn't like students. No corners, no ornaments—planes meeting at angles that did not care for human eyes. At its heart sat a low, black table—or arachnid altar—one could not tell—and on it, a lattice node as dark as gravity. Lines ran from it through the floor like veins. The nearest pylon hummed above, the vibration traveling through bone like a whispered order heard in a dream. Seraphine's field rolled across the node and raised a sheen on it, as if dew had formed on absence.
Belth drifted toward the lattice with the suicidal curiosity of the holy. "Magnificence," he whispered. "I wish to apologize to it."
"You can apologize later," Aurelius said. He did not like the way Observation skittered off the node, as if will itself were unwelcome here. He reached; it pushed back, not with force but with indifference. He had never been snubbed by matter before.
A motion in the left periphery. A whisper.
"Hold," he said, but the word was for himself. The sappers froze anyway.
From the shadow where the conduit kinked, a figure peeled off the wall. Cadian sergeant's plate. Correct boots. Correct dust. Incorrect silence. He had been a statue for a long time and had just remembered he had joints.
"Hydra," Aurelius said.
The man smiled a soldier's smile with a politician's eyes. He had a satchel charge against his thigh and the posture of someone who would cheerfully die because he'd already been paid for the death. "You brought your witch-killer. Good. Let's see which god these stones serve when you pull the noise out of them."
Aurelius didn't answer. Observation pulsed—two feints in the hands, one real throw in the hips. Conqueror's tapped a sliver into the air between them to slow the first breath of the first move without anyone realizing they'd lost it. He stepped in. The satchel came high; Aurelius took the wrist and introduced it to the wall with a sound like a lesson learned late. The knife he hadn't seen (but had felt the absence where a hand would have been because Observation is as much about holes as shapes) came low; Seraphine was there, not moving fast but arriving when the idea of motion had already done its work. The knife decided it didn't matter.
"Detonators," the traitor breathed. "Not for you. For that." He jerked his chin toward the node. "A voice under the deckplates asked for a light."
"Then we keep it dark," Aurelius said, and made him very still.
Belth's mechadendrites were already cluttering the lattice like eager birds. "Disassembly is unwise," he muttered. "Offense would be taken. We should not wish to make it angry."
Seraphine signed: Harmonics rising. The skin at her temples tight, breath measured. "My field… it's being sung into."
Aurelius felt it too—an interference pattern building where her null met the node's refusal. The pylon above thrummed, a note shifting key. If the two tones found each other at the wrong moment, he suspected the wall would un-learn the wrong lesson very quickly.
"Options," he said.
Belth's eyes clicked through apertures no human evolution had requested. "We can implode the node—shape charge, inward. Invert the energy, contain the temper."
"Radius?"
"Seven meters if the Emperor smiles. Ten if He is in a meeting."
"Do it." Aurelius pointed. "Seraphine—on my count, move through the four points." He sketched a diamond with two fingers on the air. She nodded once.
He took position opposite the node, planted the spear, and reached for the thing he had learned in the halls of the Phalanx and on the parapets of Myrridian: tempo. Observation pulsed to mark time, not targets—one-two-three-four, the lattice of seconds. Seraphine stepped where he marked; her null pulled the rising harmonic into stepped shelves, not a slope. Belth set charges, each whispered to like a child being tucked in. The sappers set their boots where Aurelius told the ground it would like them.
"Now," he said.
Seraphine took the last step and stood hard. Conqueror's came out of Aurelius like the end of a long-held breath—not a flood, a plate set upon still water. The room's intent settled. The node's sheen faltered the smallest amount.
"Light the inward," Belth hissed, joy and fear equal.
The charges didn't explode. They admitted. The lattice folded upon itself the way a man bows and keeps bowing until he's gone. A wind that did not come from anywhere sighed around ankles and left. The chamber's angles forgot to be smug. The pylon's hum found the old key again and decided to keep it.
Silence came back, honest and uncomplicated. In it, Aurelius could hear men breathe and metal cool and the little tick, tick of a mechadendrite tapping itself because joy needs somewhere to go.
Belth picked up a fragment the size of a thumbnail with three reverent claws. It looked like a piece of night given shape. "We should never have touched this," he whispered. "We had to touch this."
"We did what work demanded," Aurelius said. He looked at Seraphine. She signed: Thin. Not broken. He nodded.
Vox-beads crackled—artillery calls, void-traffic updates, the daily songs of a world learning to be a wall. Under that braid of noise came Kall's clipped Fist-voice from the Phalanx overhead: "Cadia reports multiple reaver pings at the perimeter. Probings only."
"Not tonight," Aurelius said into the bead. "They cribbed yesterday's answers and will get them wrong."
He led the file back up the conduit, the Cadians quieter now, because quiet is what men do after not dying. At the lip of the maintenance spur, the night smelled like oil and ambition. Searchlights marched on schedule. The pylon threw its knife-shadow at the same angle as before.
Draeven met them at the bastion gate. He looked at the black smear on Aurelius's spear and then at the satchel charge now made safe on a sapper's back. "Found trouble where you went looking for it?"
"It was looking for us," Aurelius said. "We taught it manners."
"Good." Draeven's eyes slid toward the pylon. "Can I go back to digging and killing now?"
"Yes." Aurelius paused. "And rotate your comms relays by hours, not shifts. Alpha wears your faces."
Draeven grunted assent, already turning away to make the order a thing the world would have to live with.
Magos Belth lingered, offering the fragment cupped like a sacrament. "For study."
Aurelius closed Belth's claw with a finger. "For caution."
Belth made a happy little servo-noise that could have been either.
They left the fragment where data would pretend to understand it. Aurelius and Seraphine climbed the bastion's stair and watched the night learn its routes. The wind off the plateau carried grit and the faintest sigh of the Eye.
Seraphine signed: Watched.
"I know," Aurelius said. "Older than Chaos. Or simply different."
She held up a hand, palm outward: Wall first. Mysteries later.
He smiled without showing it. "Walls that learn," he said.
"Men that do," she answered, and the words made a ritual he found he liked.
The vox pinged again—an encrypted ribbon with a sun-yellow seal. Praetorian. Aurelius read it in the visor light. Dorn's hand, Dorn's grammar:
To Custodian Aurelius and Sister Kest —Advance Gate doctrine to Kasr Partox and the Anchorworks. Word Bearer cadres mass in the outer approaches. Alpha interference expected.Your pairing has been noted. Duplicate it. Teach it.— Rogal Dorn
He passed the message to Seraphine. She read, then set two fingers to her breastplate: Oath.
"Silent as needed," Aurelius said.
He looked out across the lattice of trenches and pylons, the measured lights, the lines of men and guns breathing like a living fortification. His will unfolded a little, not as pressure, not as command, but as presence—a steady weight beneath the feet of a world learning to stand.
The Gate did not thank him. Walls don't. They hold, and that is gratitude enough.