'Berossus is irrelevant, Onyx. He'll shell the lower bastions to rubble and not be able to move his artillery up. No, it is Toramino that we must keep a careful watch on,' replied Honsou, turning from the battlements as fresh explosions and the roars of charging warriors rippled up from below.

'Agreed,' said Onyx, long bronze talons unsheathing from the grey flesh of his hands. 'Do you wish me to destroy him?'

Honsou had seen some of the most hideous things in this galaxy - having perpetrated a great many of them himself - but even he was unsettled by the malefic presence of Onyx. The Iron Warrior, if he could even still be called such, was a shunned figure, the daemonic presence within him making him outcast even amongst his own warriors. Though his human side still held sway in the symbiotic relationship with the daemon bound to his flesh, its diabolical presence was unmistakable.

'No,' said Honsou. 'Not yet, anyway. I'm going to break these vermin against my walls first. I can defeat Berossus easily enough, but I want Toramino to see this half-breed beat him, to know that the warsmith was right to name me his successor. Then you can kill him.'

'As you wish,' said Onyx, a barely-perceptible haze of power surrounding him.

When the creature had bound itself to Honsou's service, as master of Khalan-Ghol, it had spoken its true name as a sign of its fealty, but its pronunciation had been beyond Honsou, so he had settled for the closest approximation of the part he had been able to understand: Onyx. Honsou had seen, first hand, just how lethal Onyx could be when the warp-spawned part of him rose to the surface and he unleashed the full terror of his inner daemon.

Onyx was his dark shadow, his protector, and he could think of no better a creature to be his champion and bodyguard.

'Berossus is proud though,' said Obax Zakayo, 'and not to be underestimated. He has great strength and many warriors in his grand company.'

'Let them come,' said Honsou.

'They already do,' pointed out Obax Zakayo, gesturing over the edge of the wall.

Honsou followed Obax Zakayo's pointing gauntlet and grinned with feral anticipation.

Tens of thousands of soldiers swarmed across the smoking, cratered hell of the lower bastions, screaming like beasts as they slaughtered the few, mangled survivors of the shelling. Their victims begged for mercy, but their attackers had none to give and the carnage was on a truly grand scale.

Banners with the devotional heraldry of Berossus were raised high and sacred standards that proclaimed the glory of Chaos in its most raw, visceral aspect were planted in the bloody soil. Within minutes, disembowelling racks were set up and the soldiers who were still alive were ritually butchered before the walls to taunt those who watched from above.

'So like Berossus,' scoffed Honsou, shaking his head and watching as another hundred screaming soldiers had their entrails dragged from their bellies and looped around rotating drum mechanisms.

'What?' asked Obax Zakayo.

'He doesn't even have the wit to allow some of his prisoners to live to show his honourable mercy.'

'I fought with Lord Forrix at the side of Lord Berossus before,' said Obax Zakayo wistfully, 'and I know there is no such quality left within him.'

'You know that and I know that, Zakayo, but if Berossus had any sense, he'd try and convince the soldiers of Khalan-Ghol that he does.'

'Why?'

'Because if our soldiers could be made to believe that Berossus would be merciful, the thought of surrender might enter their heads,' answered Onyx. 'But since they now know that only hideous death awaits them should they be taken alive, they will fight all the harder.'

'To breach a fortress you need to break the men inside, not the walls. And to break a besieging army you must wear its warriors down to the point where they would rather turn their guns upon themselves than take another step forward,' said Honsou. 'We must make every one of Berossus's soldiers feel he is living beneath the muzzle of one of our cannons: that he is nothing more than meat for the guns.'

Obax Zakayo nodded in understanding and said, 'We can do that. My guns will sow the ground before the walls with their shredded flesh and the rocks will flow with waterfalls of their blood.'

'To the warp with that, Zakayo, so long as they die!' snarled Honsou, pleased to see the ember of fear smouldering within Obax Zakayo flare to life once more. 'Or else you will be down there with the scum next time. Ever since you lost those slaves bound for my forges to the damned renegades, your promises have been as worthless as the filth I scrape from my boot.'

'I will not fail you again, my lord,' promised Obax Zakayo.

'No, you won't,' said Honsou. 'Just remember that Forrix is no longer your master, I am, and I know that you are a true protege of his. He may have become so jaded that he tolerated your lack of vision, but do not think for one second that I will.'

Suitably chastened, Obax Zakayo returned his gaze to the slaughter below. 'What will Berossus do now that he has the lower bastions?' he asked.

'He will send the daemon engines,' said Honsou.

As though on cue, the monstrous silhouettes of scores of hulking, spider-legged war engines and clanking dreadnoughts could be seen advancing through the pillars of smoke and blazing wreckage. Berossus's daemonic war engines stalked through the ruined bastions, forcing their way through the fields of corpses, and began clambering across the rocks towards the battered slope of the next level of redoubts.

'Just as you predicted he would,' said Onyx, watching the approach of the daemonic machines.

Honsou nodded, listening as the ululating shrieks of the terrifying war engines echoed towards the next level of defences, hundreds of the clawed and snapping monsters hauling their spiked bulk towards the defenders above them. The next rampart was some five hundred metres above the lower bastions, many levels below where Honsou and his lieutenants watched, but the daemon engines would not take long to reach the defenders. They poured their fire into the climbing machines, but nothing could stop them.

The artillery fire from below resumed with a thunderous crescendo, the first volley exploding against the rock between the defenders and the climbing daemon engines. Boulders the size of tanks tumbled down the sloping rockface, smashing a number of dreadnoughts to flattened hunks of metal as the bombardment continued, the gunners shifting their aim as they found their range.

'Now?' asked Obax Zakayo.

Honsou shook his head. 'No, let the dreadnoughts get closer first.'

Obax Zakayo nodded, watching as the first of the spider-like daemon engines reached the next level, their massive, clawed pincers snatching up soldiers and ripping them apart. They howled as they killed, revelling in the slaughter and hurling the corpses from the battlements.

'Now,' said Honsou.

Obax Zakayo nodded and spoke a single word into his power armour's vox unit.

Honsou watched with relish as the ground of the bastions below shook and trembled as though an earth tremor had struck. Huge, gaping cracks ripped across the bastions, splitting the rock with a hollow boom that rivalled the thunder of the guns. Smoke and flames blasted from the cracks as the ground beneath the entire front half of the bastions sagged and splintered. With a groaning creak, millions of tonnes of rock exploded and detached from the side of Khalan-Gol, sliding ponderously down the face of the mountain.

Thousands of Khalan-Gol's soldiers were carried screaming to their deaths, the avalanche of rubble and debris smashing every one of the daemon engines from the mountainside, crushing them beneath the unstoppable tide of rock. Hundreds were buried beneath the mountain: their shrieking roars billowing from the rubble as their mystical bindings were smashed asunder and the daemons within them were shorn from their iron vessels.