‘My arm, you’re hurting me,’ he said.

Subha looked down at him, as though offended he was even talking to him.

‘My brothers kill, yet I am nursemaid to a mortal,’ he hissed, but the grip on Kai’s arm relaxed a fraction. Screams of pain and fear echoed from the walls, and Kai jumped in fright.

‘The way is clear,’ said Atharva, rounding the corner and gesturing for the others to follow. Kai was dragged along with the Space Marines, and the scene of carnage he faced at the end of the corridor was so utterly horrific that he retched until his throat was raw.

A host of bodies – it was impossible to say how many – lay in dismembered abandon at yet another cross-junction. Broken limbs, caved-in skulls and ruptured torsos lay scattered like the leavings of a slaughterhouse and wild arcs of blood looped over the walls in scarlet arches. That Space Marines were killers of men was a fact Kai understood on a very basic level, but to see the reality of their unleashed power was a shocking, sobering moment.

Kai had done nothing wrong, but these warrior’s Legions had betrayed the Emperor. Just by talking to them he would be considered no better than a betrayer. Yet they had saved him from death and were killing these men for reasons he could not even begin to fathom. Though this scene of butchery sickened him, Kai had sense enough to know that any chance of life was better than the death he was certain to face had he remained here.

Only two bodies had escaped the attention of the butchers that had made a ruin of more than a dozen men in a few seconds. These two soldiers had been armed with large-calibre energy weapons, and both were headless, their necks ending in cauterised stumps.

‘You shoot well,’ said Atharva as Kiron moved up the corridor.

‘Marksman first class,’ said Kiron, tapping his shoulder. ‘Only Vespasian ever outshot me in tourneys’

‘Tourneys?’ spat Tagore. ‘Why waste time on play when there are wars to be won?’

‘To hone one’s skills, Tagore,’ said Kiron, as though offended. ‘Perfected skill beats raw violence every time.’

Tagore clenched his fists over the broken stub of his spear blade. ‘Another time and I would show you the error of that belief.’

‘Pissing contests? Now? Are you insane?’ demanded Gythua.

Tagore laughed and slapped a hand on Kiron’s shoulder with enough force to draw a scowl of displeasure from the Emperor’s Children warrior.

‘Another time,’ repeated Tagore.

Kai let out a pent up breath, feeling the horrible tension that had built up in that fleeting confrontation. Their prowess as warriors gave meaning to each Space Marine, and to impugn that was the gravest of insults. In a brotherhood of equals, such posturing was friendly rivalry, but among warriors who shared no bond other than that forced upon them, it could be deadly.

‘Where to now?’ said Tagore. ‘The net will be closing.’

‘This way,’ said Severian, taking a passageway that led upwards.

‘You knew the Custodian’s mind,’ said Tagore. ‘Is the Wolf right?’

‘He is,’ confirmed Atharva. ‘Severian’s awareness serves him well.’

Again they set off, and each time the Space Marines met resistance, they demolished it with efficiency that would have been cruel had it not been achieved with such clinical precision. Only the three World Eaters seemed to take any pleasure in the violence, but even that was more about the display of prowess than any base enjoyment of slaughter.

Onwards and ever upwards they pushed, sometimes fighting their enemies, sometimes avoiding them. Severian and Atharva had knowledge of this prison that was more than the equal of the soldiers tasked with preventing their escape, though Kai could not imagine how they could have come by such information.

‘Where are the Legio Custodes?’ asked Kai, in a moment between desperate flight and visceral bloodshed. None of the Space Marines had an answer for him, though he saw the same question had occurred to them all.

‘They are not here,’ said Gythua. ‘That is all that matters.’

‘They are heading to Prospero,’ said Atharva. ‘If they are not there already.’

‘Prospero?’ said Kiron. ‘Why?’

‘To slay my primarch,’ said Atharva, and Kai heard the resignation in his voice.

Even Tagore had no reply to that, and Kai sensed their shock at so bald an assertion. Clearly there was little love lost between these warriors, but to hear so terrible a thing spoken aloud reminded them of what they had lost by being brought here.

‘Is such a thing even possible?’ asked Kai.

Atharva looked at him as though he had said something profoundly stupid, but the moment passed. ‘Regrettably, it is entirely possible. We are all wrought from the raw matter of stars and the Great Ocean, but even stars can die and oceans turn to dust.’

‘How do you know this?’ asked Asubha.

‘I know it because Primarch Magnus knows it,’ said Atharva.

No more was said on the matter, and their brutal, bloody ascent to the surface of the world continued. Where ambushes were laid, Severian would strike from the shadows. Where attacks came upon them without warning, Tagore and Asubha would counterattack with furious strength. Where men with guns filled the passages with fire, Kiron would drop them with pinpoint shots that boiled brains within skulls before bursting them like overfilled balloons of blood and brain matter.

When barriers were erected to bar their path, Gythua would wade through hails of gunfire to batter them down, shrugging off the shots of his enemies as though they were of no more consequence than insect bites. Dried blood slathered the Death Guard’s chest, and a charred crater the size of Kai’s fist had been bored in his side. Armoured doors presented no obstacle to them, for Atharva possessed a golden ring, like that worn by Saturnalia, which unlocked every portal closed against them.

As the last such shutter was opened, Kai was bathed in the most beautiful illumination he had ever seen, a light he thought he had forgotten, the light of Terra’s sun. Kai’s augmetics recognised the filtering effect of an integrity field on the sunlight and realised they were in a mountainside embarkation bay. A row of gold-trimmed shuttles and landers lined one of the cavern’s walls, and a number of less ornate craft hissed and vented pressurised gasses as servitors and loaders cleared their c argoholds and stowage bays.

‘Move,’ said Severian, looking back the way they had come. ‘They know where we are now, and aerial units will be scrambling soon.’

Half carried, half dragged by Subha, Kai and the others ran into the hangar. Surprised faces turned towards them, ground crew, tech-priests and menials. None of them dared challenge the intruders in their midst, for it was clear that these bloodied daemons were butchers of men.

Gythua led the way, a limping mass of bloodied muscle and scar tissue. He growled with a mixture of pain and anger, leaving a spotty trail of sticky droplets in his wake. Kiron ran alongside him, ready to help his friend should he falter yet keeping his hands to himself lest the proud Gythua take offence. Severian followed and Tagore went with him. Asubha ran to the nearest craft, a sleek cutter that had not long touched down by the heat haze rippling around its engine vanes.

‘Can you fly it, brother?’ shouted Subha.

‘This thing? In my sleep,’ replied his twin.

A tech-priest in crimson robes with a rotating series of eye lenses attached to a radial disc attempted to intervene, but Subha put him down with a casual swipe of his spear. Even as the shorn halves of the Martian fell, the body’s upper half continued to harangue the World Eater as a burst of panicked binary static screeched from his shoulder-mounted augmitters.

Alarms shrieked from above, and an armoured blast door began rumbling across the wide rectangle of open space visible through the integrity field. Spinning warning lights threw stark shadows and a hellish orange glow through the hangar as the ground crew who could flee took to their heels.