'But'

'Do it now, then lock off the vox-channels on the whole level.'

The legionnaires bounded up the stairwell, tightly hugging the wall as they rounded each successive corner with their bolters always trained up the next flight of stairs.

Beyond them lay the breadth of the Pylon Array.

Through the mesh of the inside wall, the Alpha Legionnaires could see the glossy black stone of the constructed xenos artefact, and feel the low hum of aethereal energies. The stone Pylon thrust up through the base's superstructure, with entire installation floors and sections built around it.

Sidling along the mesh-covered stone, Volion signalled. Footsteps.

'Auguramus?' Omegon growled.

'Only a tech-priest, lord,' he replied. 'Ahh, it's my assistant and her bodyguard.'

Squad Sigma held their positions, each legionnaire silent and ready. Volion slid along the wall on his pauldron and held there on a small landing. An aged female Mechanicum priest appeared around the corner around her head, keeping sparse lengths of straggled grey hair in check, was a metal band. A third cybernetic eye was set in the band, and the tech-priest was using it to read a data-slate, while carrying several others in her free arm.

Grabbing the priest in his vice-like grip, Volion pulled the woman past him and hurled her off the landing and down the flight of stairs. Her servitor bodyguard reacted immediately, bringing a chainblade arm attachment to roaring life and swinging it at Volion, but the legionnaire batted the drone back. He followed up with a sudden charge, crushing the servitor into the wall with his armoured shoulder.

The chainblade bleated to a stuttering stop and the legionnaire pulled back, allowing the guard's broken body to slump to the floor.

Omegon watched Arkan check the crumpled body of the priest. It had been a long fall. She was dead; her neck was broken.

'Auguramus. Open accessway DT367b.'

In answer, the clunk of a locking mechanism cleared and Setebos looked through the gap between the auxiliary opening and the wall. Joining him on the penitorium level landing, Omegon peered through the crack as well.

The accessway opened out onto a broad deck serviced by the locked lifter, and several passages and stairwells ran off the deck, leading to other sections of the installation. Opposite was the formidable black gate of the psi-penitorium. Two skitarii sentinels stood either side of the bulkhead in their rust-coloured robes, each bearing a bionic weapon replacement instead of a right arm. Their faces were ghoulish rebreather masks with clicking telescopic opti-sockets.

The gate opened and Omegon could hear the screams of madness and the moans of distress echoing down the wide passageway beyond. Two further skitarii gaolers pushed a tall cage on rails down the passage and out through the gate. The black metal of the cage sizzled with energy; within was an emaciated woman, naked and pale. She was curled up foetus-like in the cage bottom, rocking and groaning in pain. One of the skitarii slashed the side of the cage with the length of his electro-flail, drawing a yelp of agony from the psyker prisoner.

'Sergeant,' Omegon said. 'Take your men up the lifter shaft. Master Echion is about to call for support from the Legion dormitories. Ensure it never reaches him.'

Setebos nodded his understanding and had Braxus remove the port cover of a devotional maintenance duct. One by one the Alpha Legionnaires disappeared into the wall.

'Volion. Charmian. You're with me,' Omegon said.

He took Charmian's bolter and fell into step with Volion behind him, as they left the stairwell and made their way across the broad deck. As they approached the psi-penitorium gate, the two impassive skitarii guards stepped forward to bar their way.

Charmian played his part well. Not slowing, and with Omegon and Volion flanking him like an officer escort, the legionnaire walked straight at them.

'Prisoner inspection,' Charmian told them. 'You already have your clearance from the Artisan Empyr. Don't waste my time.'

After a moment's hesitation, the Mechanicum warriors parted and the gate rumbled open. Charmian didn't break his stride. With Omegon and Volion, the legionnaire marched down the wide, dismal passage beyond, being careful not to stumble on the floor rails. After passing through two more gates and between two more pairs of sentinels, the Alpha Legionnaires entered the main penitorium.

At the centre of a runebank hub the trio encountered a crew of lex-mechanics, skitarii guards and a heavily augmented skitarii tribune, who sat wired directly into an observation throne with a spread of optics and motion-tracking matrices sprouting from his grisly head. Around the hub chamber, a series of railed passages led off into darkness. Each echoed with the collective moans of imprisoned psyker slaves.

'Where is my prisoner?' Charmian demanded as he entered. The tribune gave the approaching legionnaires a gaze of blank confusion. 'Not prepped. Not caged?' Charmian growled. 'I was assured full cooperation by the Artisan Empyr.'

A skitarii sentinel with a flamer for an arm stepped out from one of the adjoining passages. Staring at Charmian with his whirring mask optics, he silently indicated that the Space Marines should follow him.

With the pilot flame from the skitarii warrior's weapon lighting the way like a flickering candle, Omegon marched past the dreadful cries of tormented witch-kin in the psi-shielded cells. The black shielding of the cells sapped the witchbreeds of their potency, and afflicted them with a soul-draining agony.

At the bottom of the passage, the skitarii came to a halt. Two of his fellow sentinels were standing outside an open cell. They had positioned one of their rail cages at the entrance, and were manipulating a set of controls mounted on the wall. They increased the energy flow running through the psi-shielding and the prisoner threw herself from the cell and into the cage with a pained screech.

Like an animal, Omegon thought.

Out of the unbearable field, the psyker was clearly relieved. She collapsed in a heap, breathing heavily. Stripped naked by her captors, Omegon could see her ribs and the bumps of her spine through her pallid skin. The crackling cage, although made of the same draining material and visiting a similar form of debilitation on the prisoner, couldn't deliver the same intensity as the cell. This gave each prisoner a moment or two of respite and a motive to transfer voluntarily from one to the other it was a smooth operation and, although sickened by what he saw, Omegon was impressed by the system's economy.

Sealing the cage, the skitarii began pushing it along the rail towards the hub. The Alpha Legionnaires remained close to the sentinels and their cybernetic guide, until they crossed the third intersection.

Stepping up behind the guide, Volion silently slipped the tip of his combat blade under the skitarii's forearm fuel line. With the weapon's promethium supply cut off, the legionnaire seized the sentinel in an arm lock and plunged the full length of his blade through the rust-red hood and down into the warrior's brain. However, Charmian wasn't as delicate or precise as his brother legionnaire; grabbing one of the two gaolers from behind, he hefted the flailing deadweight of flesh and machinery into the air and slammed it down on the passage floor, expecting the cybernetic warrior's neck to snap across the rail.

But it did not. Surprised but fully functional, the sentinel brought its stubby volkite arm attachment up to meet the hulking Space Marine standing over it. Charmian's helmet opened up by the shot dashed the ceiling with broken ceramite and fragments of skull.

Volion cursed and brought his boot down savagely on the sentinel's mask, and this time its reinforced alloy neck gave a satisfying snap over the rail and the weapon slumped back to the floor.

Omegon wasted no time in dispatching the third warrior. Thrusting his gauntlet forward, the primarch plunged his armoured fingertips through the sentinel's flesh and augmented organs, and allowed the dying wretch to sink to the floor.

With her gaolers dead about the cage, the prisoner hauled her weakened body up the crackling bars. She rested her forehead against the dark metal and gave Omegon her big, underworlder eyes.

'Xalmagundi. You look unwell.'

'Get me out... of this bloody cage...' she hissed.

Smashing the lock mechanism with his bloodied ceramite fist, Omegon freed the psyker and helped her from the draining influence of its confinement.

Down the passage, they heard the grumble of the hub security gate opening. Peering up through the gloom, the primarch could make out the unmistakable forms of Alpha Legionnaires stood before the skitarii tribune and his runebanks.

It was Ursinus Echion, and a two-man escort.

The Librarian seemed to be berating the tribune, Omegon guessed, for being summoned to the penitorium unnecessarily. Then, in mid-sentence, he stopped. Turning slowly, he peered down the dark passage. The Librarian had clearly sensed something: in all likelihood, Xalmagundi's presence raw, potent and unchecked. He took several cautious steps towards the passage opening. His copper face creased with fury.

Omegon and the psyker melted into the shadows, followed swiftly by Volion.

'Summon the rest of your skitarii,' Echion called back at the tribune. 'You have an escaped prisoner. Sound the alarm!' As deep klaxons rang through the hub, Echion turned to his Alpha Legion escorts.

'Call a squad down here. Now.'

DELTA.

Operatus Five-Hydra: Elapsed Time 2/004.66//TPATenebrae Installation Unslipping his bolt pistol from its belt holster, Echion strode up the passage. The tribune had hit the general alarm and the hub became a wash of bloodshot light and ear-splitting noise. The psyker slaves screamed and shrieked in their cells, banging on the thick, black metal of the doors and howling like agitated animals.

As he and his escort reached the bodies of Legionnaire Charmian and the skitarri surrounding the breached cage, Echion scanned the gloom with his pistol. The cell door at the bottom of the passage was wide open...

Moments passed. The Librarian seemed unsure.

'Where's that squad-'

Before he could finish, the Space Marine nearest to him dropped his bolter and began clawing at his own battle helm. Echion grabbed his arm to steady him, but the ceramite began to crumple under his gauntlets. Some terrible force was crushing the legionnaire inside his armour like a great invisible vice, his pauldrons and chestplate buckling with a metallic groan.

Echion turned to find his other escort pinned against the wall, gurgling and choking.

Both of the stricken warriors screamed, and then fell slackly to the floor in a crushed, bloody heap. Echion whirled around, his pistol ready.

'Show yourself!'

Echion was suddenly struck by an incredible force, with such ferocity that his armour caved in across the plastron. He crashed through the cage and became entangled in the crackling bars, which proceeded to creak and contort around him. Another invisible blow sent him spinning boots-over-shoulders through the darkness.

He cracked off a succession of blind shots from the floor, but the dreadful unseen force smashed into him again and again, hurling both him and the misshapen cage down the passage and cracking them against the ceiling.

A final burst of automatic bolt-fire ran the pistol dry, but before the Librarian could reload the weapon he was torn from the wreckage of the cage by an impact that split his already crumpled chestplate. The invisible blow sent him through the air and into the deep darkness offered by the open cell door.

'I'm here, Alpha.' A slender silhouette presented itself in front of the opening, before willing the cell door to slam shut with a metallic boom.

Ursinus Echion pushed himself painfully to his feet.

'Janic, respond,' the Librarian coughed into his vox-link before spitting blood at the filthy cell floor. 'Code Crimson. Repeat, Code Crimson.' He changed channels. 'Strategarch Mandroclidas, respond.'

No answer came. He switched again. 'Artisan Empyr? Does anyone read me?'

He glanced about in the absolute darkness of the cell, sweat beginning to bead his brow. He shuffled over to the door. Closing his gauntleted fist, he began to pound on the dark metal. The psi-shielding was crippling the Librarian. There was no response to his vox-calls. He was alone in the dark.

Or at least, he thought he was.

Omegon had seen enough. Given time, he was sure that the psyker would find a way out of even this prison...

'It seems my concerns were warranted, Master Echion.'

The primarch watched the Librarian's face change rapidly from the shock of realising that he was not alone in the cell, to alarm as he recognised the voice addressing him. Through his helmet's augmented vision Omegon observed the psyker's shift in demeanour.

Echion put his back against the withering wall of the cell. Without the advantage of his own helmet optics he could not make out the primarch in the nullifying darkness.

'My lord,' Echion said, trying to remain calm and keep the anger and frustration out of his voice. 'I do not understand. A dangerous psyker is loose. The Pylon Array is under threat, exactly as you predicted.'

'Not our finest hour, is it Echion?' Omegon told him honestly. 'The only consolation you might take from this is that you were infiltrated by your own.'

'Infiltrated...' the Librarian repeated, 'by the Alpha Legion?'

'Yes, Echion. By the Legion.'

'Is the base compromised, then?' Echion asked, his eyes darting in the blackness.

'In every way imaginable.'

Echion's shoulders sagged. The Librarian was beginning to understand.

'I'm deeply sorry if I failed you in this, my lord,' Echion said. 'Our enemies-'

'Our enemies are no longer your concern,' Omegon interrupted him. 'No one will ever find a single shred of evidence that this installation ever existed.'

'You're going to scratch the base?'

'The base, the xenos technology, and all who could speak of its existence. Many will suffer the ultimate price for this failure.'

The Librarian nodded. 'I understand. Might I ask-'

The darkness lit up with the bark of bolter fire.

The bolts tore into Ursinus Echion, spraying blood and ceramite fragments across the walls. Only when the Librarian's body hit the floor did the fusillade cease, leaving Omegon and Volion in the darkness of the cell, the crash of automatic fire still ringing in the enclosed space.

'Xalmagundi,' Omegon called. 'Get us out of this bloody cell.'

The cell door gave a tormented creak before being ripped from its hinges and spinning off down the passageway towards the chaos of the penitoria hub, where Omegon could make out ranks of alarm-rallied skitarii attempting to secure the block. He stepped out of the cell, flanked by Volion.

Emerging from a side passage, the naked Xalmagundi all pallid skin and bone joined them. As an underworlder she seemed quite at home in the darkness. She gestured up the corridor towards the waiting tech guard.

'You wish me to destroy them?'

'Of course,' Omegon said, rolling a dead sentinel out of its tattered robe. 'But first, put some clothes on.'

Operatus Five-Hydra: Elapsed Time 1/-214.77//XXUXX Legion Strike Cruiser Upsilon 'And then we fire the detonators,' Krait said with confidence across the midnight sheen of the table.

'No,' the primarch corrected him. He tapped a series of studs on the arm of his throne, and the obsidian surface blinked to become a document of glyphs and symbols flashing by. Letter by letter, numeral by numeral, the document was being decrypted.

'Don't underestimate Janic. Echion's specialisation gives him primary responsibility for the array, but he'll leave security to Arvas Janic.'

The gathered legionnaires examined the commander's service chronicles as they spooled past.

'Know the mission, know the man,' Omegon instructed. 'And he's led a host of them himself. As you can see, this was always the history of a legionnaire destined for captaincy: several awards from previous commanding officers, including Thias Herzog and Ving Neriton; commendations for both innovation and constancy under fire. Veteran's crux. The Ouroboron. Victories at Ignatorium and Five-Twenty Nine. Had some bad luck with the K'nib at Selator Secundus, but didn't we all, and lost three legionnaires during the eradication of the Thorium Abominiplex which is unsurprising given how many troops were lost by Lord Mortarion. Still, these are the service annals of a ruthlessly efficient and inventive commander. A record of which the Legion is justifiably proud. It's almost a shame we are going to have to ruin it.'

'Only three of these were garrison duties, though,' Isidor indicated, running his finger across the glassy surface. 'A submerged "halting site" whatever that is on the ocean world of Bythos...'

'Tactical outpost 'Epsilon/Loco', masquerading as a giga-container, routinely exchanged between bulk lifters over Isstvan IV,' Setebos interjected.

'And a Class-3 listening post in the ruined Gardens of Ptolemy on Prandium,' Isidor continued.

'None of which were compromised,' Omegon reminded them. 'His security logs for Tenebrae confirm a mix of sentry points and alternating patrols that he has implemented for the Geno troops at his disposal. He will not trust these alone, however, and will have a contingency strategy established between his own legionnaires for a perimeter breach he will not rely upon allies or operatives, if things get out of hand. With his own squads he favours staged fallbacks, tactical demolitions, promethium cleansing, gauntlet approaches, mined cut-routes, wired bulkheads and blackouts.'

'As soon as Janic knows the base is under attack,' Setebos extrapolated, 'his legionnaires will likely be drilled to lock it down and restrict the penetrating force to non-essential sections.'