Alpharius fired again with a shout of disgust, pulverising the Word Bearer’s misshapen head. The other legionary spun around and fired, his burst catching Alpharius in the gut. A cable ruptured, artificial muscle bundles fraying in a welter of white sustaining fluid.

A Raptor surged past Alpharius, bolter blazing, opening up a line of bloody craters across the Word Bearer’s chest. The traitor swung his bolter like a club, but the Raptor was too quick, deftly deflecting the blow with his own weapon, before repeatedly smashing his elbow into the side of the Word Bearer’s helm. The Raptor hooked a foot behind the traitor’s leg and tripped him with another blow to the head.

One foot on the Word Bearer’s chest, the Raven Guard warrior fired, bolt after bolt punching through the traitor’s armour, coating the Raptor’s greaves with gore.

‘Move on,’ said Dor, pointing towards a sealed archway on the opposite side of the chamber.

Looking around, there were no Raven Guard casualties. Alpharius counted five dead Word Bearers, another of them showing bestial, twisted features similar to the one he had slain.

‘Let’s not think about that too much,’ said Dor, guessing Alpharius’s thoughts from his posture. ‘According to the pulse survey, there’s a reactor two levels down, almost directly below us. Look for a stairwell.’

It was impossible for Alpharius not to think about what he had seen. There had always been rumours. Less than rumours, more fanciful soldiers’ tales. Ships had been lost and found with their complements ravaged by some horrific power. Every legionnaire who had spent time in the warp had a story about a strange dream or discomforting occurrence. Alpharius had half-glimpsed bizarre things on the cusp of wakefulness while in warp transit and Legion command had never directly denied that the warp was inhabited. Seeing the contorted faces of the two dead Word Bearers reminded Alpharius of those vague dreams and he wondered just what was happening to the Legiones Astartes who had sided with Horus.

Another corridor led them into a mess hall that ran the width of the facility, nearly seventy metres long. A firefight was already raging when they arrived. The air was filled with criss-crossing salvoes, bright sparks of bolt propellant and fiery detonations reflecting from steel-topped tables and laminated shelves. The roar of bolters and ring of impacts was deafening. The Word Bearers had taken up positions behind overturned tables and in the galley at the far end, and were exchanging fire with two squads of Raptors pinned down at a set of double doors opposite Alpharius.

A burst of shots greeted Sergeant Dor as he ran into the room, bolter on full automatic fire. He heaved over one of the long bench tables and hunkered behind it, splinters of metal spraying around him, bolt detonations sparking across his armour.

Without hesitation, the Raptors piled into the hall from behind Alpharius. The first was taken off his feet by a plasma bolt that melted through his chest plate and incinerated his innards. The Raptors exacted instant vengeance, blazing away at the plasma gunner, the Word Bearer’s armour and a glass-fronted cabinet behind him exploding with hits.

‘Flank move, squad three!’ The order was snapped out by one of the Raptors as he bounded up on to a table with a grenade in hand. He lobbed the grenade over the serving counter separating the hall from the galley. A blossom of fire erupted in the heart of the galley, setting off a chain of secondary detonations from ruptured power lines.

The black-clad Raptors surged down each side of the hall, racing forwards without firing. Two more were sent tumbling by the volleys of the Word Bearers but the dark-armoured legionaries pounded on, ignoring their casualties.

‘Keep up, old fella,’ one of the Raptors laughed at Dor as he sprinted past the sergeant.

‘Cheeky bastard,’ snarled Dor, powering himself over the fallen table, bolt-rounds blasting down the hall from his weapon. ‘Support fire!’

Alpharius sidestepped into the hall and squeezed off a salvo of five rounds, targeting a Word Bearer bringing a plasma gun to bear from behind a trolley stacked with water jugs. The ewers disintegrated into shards and silver slivers, the Word Bearer forced to dive out of sight, the fresh red paint of his armour pockmarked by several direct hits. The rest of the squad dashed into the hall and took up firing positions, bolt-rounds hammering into the metal counter and tables shielding the Word Bearers.

The Raptors reached the far end of the hall, pulling free combat knives to hurl themselves at the waiting Word Bearers. Alpharius saw one of them shredded by the combined fire of three traitors, moments before his squad-brother vaulted over the counter, his bolter firing point-blank into the face plate of a Word Bearer. The Raptor slashed his knife backhanded through the throat seal of another even as his left pauldron shattered in a hail of ceramite fragments from a bolt impact.

The Word Bearers had not expected the sheer swiftness and ferocity of the Raptors’ attack. Black-armoured legionaries were pouring between the shelves and cupboards of the galley, overwhelming the traitors with bolter and knife.

At a word from Dor, the squad started forwards, ready to cover the Raptors if they were forced back. There was no need for such caution. Alpharius saw a Word Bearer go down, bludgeoned by the bolters of three Raptors. Another traitor was lifted off his feet and hurled bodily into the power cables exposed by the grenade, sparks and arcs of lightning scorching across his twitching body.

The last time Alpharius had seen anything like it had been the World Eaters’ charge into the Salamanders at the dropsite. That had been raw carnage on a scale he had never imagined possible. The fight in the mess hall was far less of a spectacle, but the lethal efficiency of the Raptors was no less impressive.

He pictured the superhumans ahead of him in the colours of the Alpha Legion, tearing through Ultramarines or Dark Angels. There was an irrepressibility about the way they fought, a disciplined fury coupled with extraordinary speed and precision. And they were just fresh recruits. Alpharius imagined the Alpha Legion descending on Terra with fifty thousand such warriors, hardened by previous battles, with the canniness and guile they would learn from the primarch.

That was a force Horus would respect. Suddenly, Alpharius realised just how important his mission could become and why he had not yet received orders to destroy the gene-tech. This was not about stopping the Raven Guard. This was about strengthening the Alpha Legion.

The hall fell quiet, the death cry of the last Word Bearer quietly ringing from the steel walls. Alpharius moved into position to secure another doorway ahead, while the Raptors moved amongst the traitors, wordlessly ensuring they were all dead with knives to the back of their necks.

‘New orders!’ barked Dor. ‘The reactor has been set with charges. We’re leaving now. Thunderhawks for extraction at grids seven-sixty and seven-ninety. We have sixty seconds. Move!’

‘That’s it?’ said Alpharius, before he could stop himself. ‘We’re done?’

‘Strike and withdraw, you know the procedure,’ the sergeant replied. ‘Mission was to destroy the station. In fifty seconds, we will have been successful.’

The Raptors needed no repeat of the orders. Squad by squad they fell back from the galley and across the mess hall. Alpharius retreated, still keeping a wary eye for any counter-attack.

‘Are the enemy eliminated?’ he asked.

‘They will be when that reactor explodes,’ Dor said with a laugh. ‘No time to hang around.’

They withdrew to the corridor along which they had advanced and clambered out of the shattered windows. A stream of black-armoured legionaries was pouring back into the sandstorm, disappearing from sight. Alpharius felt grudging respect for the Raven Guard as they melted away as quickly as they had appeared. Forging through the sand drifts, he glanced back but the facility was now enveloped in the dust storm and obscured from sight. Ahead, his locator locked on to the signal of a descending Thunderhawk. Ramp open, the drop-ship plunged down into a dune, adding to the swirl of sand.