'Be still,' he warned.

Just as he had begun to think they had not been detected, a spear of phosphorescent light streaked skyward, closely followed by a second. Both burst within seconds of one another and the plateau was suddenly illuminated by twin suns burning brightly as they slowly descended on small grav-chutes.

A cry of alarm was raised high above them and Honsou cursed aloud this time, uncaring of who heard him.

'Damn you, Polonas!' snarled Honsou, wrenching the ancient warrior from the ground. The metal of the bionic leg was wedged tightly and it was the organic components of the limb that failed first, tearing free in a wash of blood as Honsou ripped Polonas from the ground.

Polonas grunted in pain, the accelerated healing mechanism of his body stemming the flow of blood from his severed leg in seconds. Honsou shucked the man onto his shoulders and shouted, 'Iron Warriors, go! As fast as you can!' He heard the unmistakable cough of mortar fire.

Honsou knew that the first rounds would be for ranging purposes, but there would be spotters on the wall to direct subsequent volleys. They had to make as much use of this time as they could. The strobing light of the two sunflares cast lunatic shadows across the cracked ground and it took all Honsou's skill not to lose his footing as he raced from the base of the mountain. The ground rocked as mortar shells burst ahead of them, scything deadly fragments in all directions, but they were landing too long. The height of the mortars was working against the Imperial gunners now. Their elevation gave them longer reach, but also meant that it was impossible to engage targets within a certain range.

Perversely, Honsou knew they had been safest where they were, but also knew it was only a matter of time until troops were sent to flush them out. It was unlikely the Basilisks would join the fight, as it would be a waste of ordnance to engage so few targets with so remote a chance of hitting.

Another volley slammed into the ground, closer this time, and Honsou stumbled to his knees, just barely keeping his balance with the weight of Polonas on his shoulder. More sunflares exploded overhead and now small arms fire began bursting around them. Las-bolts vitrified the dust and heavy bolters churned the ground. He felt an impact graze his shoulder and another clip his thigh, but these were little but annoyances: his armour was proof against such weaponry.

Heavier impacts blasted into the ground beside him and he swore again as he realised that the defenders had managed to bring some heavy weaponry up to the firing step. A bolt from a lascannon hammered into the ground beside him, cracking the earth and flashing the dust to vapour.

More shells landed and this time Honsou was thrown to the ground as a mortar shell burst less than five metres directly above him, spraying him with razor sharp shrapnel. Red runes winked into life across his visor as the spirit within his armour registered breaches in its structure. Honsou could feel the stickiness of blood briefly run down his leg and back before his enhanced metabolism clotted the wounds.

He offered a brief prayer of thanks to the gods for sparing him. Power armour was amongst the best protection a warrior could have, but even it had its limitations. He reached over to grab Polonas and realised why he had been spared.

The veteran's back was laid open to the bone, his thick ribs and spine glistening and red. His head was a mass of gristle and bloody flesh, pulped grey matter pouring in a glutinous flood from his shattered skull. Honsou shrugged and tapped Polonas's Iron Warriors' icon on his shoulder plate in thanks for saving his life, then picked himself up from the ground.

Honsou pushed himself forward and, freed from the weight of Polonas, was quickly able to outdistance the mortars, pounding across the cratered ground in a lumbering sprint.

Shells continued to land behind him, but the gunners on the walls were firing at phantoms now, their targets having escaped their wrath. Honsou slowed to a jog and counted in his men, coming up one short. Aside from Polonas, only one other warrior had fallen. Honsou considered they had been lucky.

More sunflares continued to turn the valley's night into day, but the Imperials were simply wasting shells now.

Honsou strode through the picket lines protecting the digging parties, satisfied at the progress the slaves were making. The ground was dusty and hard-packed, but given the right threats and impetus, the slaves were working fast enough.

Over two thousand men dug the barren soil of Hydra Cordatus, creating a trench that ran from the eastern edge of the valley wall to a point mapped out by today's foray of the prisoners at the extreme range of Tor Christo's guns. Here the trench bent southwards, following the curve of Tor Christo's curtain wall.

The earth excavated from the trench was piled on its outer edge, on the side facing the fortress, providing a ready-made fire step and protection for the diggers. Once the trench had been completed, the Iron Warriors would build more permanent fortifications along its length, adding linked bunkers every fifty metres and laying minefields of their own.

Honsou jumped across the trench, nodding in acknowledgement to men from his company as they supervised the labouring slaves, ensuring everything was constructed to their satisfaction. The work was progressing at speed and, barring interference from the Imperials, the trench was sure to be complete before morning.

He moved easily through the swarming throng of bodies engaged in digging and stockpiling supplies ready for the push towards Tor Christo. Slaves either dragged enormous flatbeds of shells and explosives forward or sweated under the load of adamantium sheets to form roadways for heavy artillery and tanks. Others were arranged into chanting groups gathered around hastily emplaced shrines to the Dark Gods, their mutterings overseen by one of Jharek Kelmaur's sorcerers.

Bright arc lights were erected on baroque towers of iron, each placed at points decreed by the sorcerers to create some form of cabalistic arrangement. Quite what this would achieve, Honsou was unsure, but he reasoned that it couldn't hurt to appease the gods, whatever measures were used. Honsou honoured the Dark Powers of Chaos, but preferred to rely on the strength in his sword arm and the explosives in his artillery to win campaigns. To rely on Chaos was to invite disaster at the capaciousness of the gods. Had Angron himself not failed on Armageddon by doing just that?

He saw the Warsmith's pavilion set upon the rocks on the eastern flank of the mountains. Its bronze poles supported billowing steeldust fabric patterned with twisting, chaotic designs that enraptured the eye and held its fascination until reason itself became lost forever within the swirling significance that remained forever elusive. Honsou had learned never to allow his gaze to be lured into the foul pattern and kept his eyes firmly fixed on the figures that reclined beneath its treacherous design.

The Warsmith sat on an enormous throne, carried from lost Olympia and said to have been crafted by the holy Perturabo himself. The Warsmith claimed it was a gift from the primarch after the fighting on Tallarn, though Honsou doubted that their monstrous, daemonic progenitor would have been so generous after that particular campaign. Beside the hulking, sickening presence of the Warsmith stood the dead-faced Forrix, reading out lists of numbers and displacements of troops from a bone-rimmed data-slate.

Behind the throne stood Jharek Kelmaur, the sorcerer whose pronouncements had led them to this world. The sorcerer's armour was embossed with gold and silver, the traceries and patterning bewilderingly complex. Skulls decorated his greaves and cuissart, and his breastplate was moulded in the shape of Adonis-like musculature. He wore no helmet and his features spoke of a sly cunning: a lipless mouth and sewn-up eyes, set within a swept-forward brow. His pale skull was hairless and tattooed with bizarre symbols that seemed to writhe with a life of their own.