'Full speed! We must close with the monster before we suffer a similar fate!' replied Daekian.

Less than a hundred metres separated them now and Daekian could make out the terrible damage Princeps Fierach had managed to inflict on this warp-spawned beast before being dragged to his death. Huge steel plates were crudely welded across the Dies Irae's midsection and all manner of auxiliary mechanisms had been grafted to its legs to allow it to move.

Fire from the gatling blaster blasted off more of its void shields and as Daekian saw a single shell explode against its upper bastions, he knew that the beast was stripped of its infernal protection.

He pushed the Honoris Causa forward and raised the volcano cannon.

'This is for Princeps Fierach,' he snarled and fired.

He watched the searing beam of unimaginably powerful energy streak towards the Dies Irae's head, knowing, even as he fired, that the shot was true.

His triumph turned to disbelief as the beam struck on a void shield, repaired at the last second before impact. The Dies Irae ground its torso towards him, the white-hot barrel of its plasma weapon aimed directly at him.

'Evasive manoeuvres!' he bellowed, even as he knew it would be too late.

The Honoris Causa lurched sideways as the plasma bolt fired.

Princeps Daekian was almost quick enough. Almost.

The shot impacted on the Warlord's volcano cannon, instantaneously vaporising the weapon in a seething ball of plasma. The explosion ripped up the Titan's arm, the adamantium structure flashing molten in a heartbeat.

Daekian screamed in agony, convulsing as the flashback from his arm's destruction flared along the mind impulse link. Blood streamed from his nose and ears, but he kept true to his course, striding towards the hazy outline of the Dies Irae through the smoke filling the command bridge.

He reached the walls at the same instant as the Dies Irae, the raised ground inside Vincare bastion bringing him level with his foe's head. The Pax Imperator circled around to his right, its carapace running with plasma fire and limping as its leg joints trailed streamers of white sparks.

Daekian lashed out with the Honoris Causa's one remaining arm, his battle claw slamming against the Dies Irae's chest. The massive Titan rocked back under the powerful blow, swinging its arm against the lip of the bastion and smashing through the rockcrete and hammering into the Honoris Causa's upper leg.

Daekian felt the leg crack and heard the screams over the vox from the engineering decks. He had moments at best.

He swiped again at his gigantic foe, ripping the armour plating away from the Dies Irae's belly as it pummelled his wounded flank with its arms. It lurched backwards, attempting to protect its now vulnerable reactor.

The horrendously damaged Pax Imperator charged into the fight, its chain fist ripping through the upper bastions of the Dies hae, its blade shrieking as it tore downwards towards the war machine's bridge.

The Dies Irae's barbed tail swung and pulverised the knee joint of the Pax Imperator, shaking loose its chain fist and staggering the mighty god-machine.

Daekian watched the Dies hae turn and hammer the barrel of its plasma annihilator into the bridge of the Pax Imperator and fire at point-blank range.

The upper half of the Reaver vanished in a searing blast, enveloping the two battling Titans with liquid fire. The remains of the Pax Imperator crashed over the walls of the bastion into the ditch, huge plumes of black smoke trailing from its burning hulk.

But its death had given Daekian the opening he needed.

He rammed his battle claw against the heat-softened midsection of the Dies Irae's reactor chamber, through the wound first opened by Princeps Fierach. He roared as he punched through into his foe's guts, gripping its nuclear heart in his iron grip and crushing it with all his might.

Honsou watched the battle between the enormous war machines through the drifting haze of smoke, willing the majestic form of the Dies Irae to smash its inferior foes to scrap metal. He sheltered in the lee of the breach, his armour dusty and bloodstained.

His frustration grew with every explosion above him. They could not force the breach like this.

He watched as the leviathans struggled on the far bastion, their battle shaking the ground as though a powerful earthquake gripped the world. 'Forrix!' he yelled over the din of shells exploding at the crest of the breach. 'One way or another, this battle will soon be over. It is time to withdraw!'

Forrix shook his head, sneering. 'I should have known your cowardice would finally come to the fore! We stay and take this breach.'

Honsou felt his anger flare and gripped Forrix's armour, shouting. 'We have to go! The attack has lost its momentum and the enemy will be regrouping behind the walls. We only reinforce failure if we stay. There will be another time!'

For a second, Honsou thought Forrix was about to rebuke him again, but the fury drained from his eyes and he nodded, turning without a word and scrambling down the breach.

Honsou followed him and the Iron Warriors retreated from the walls, falling back to the ditch in disciplined groups. As he clambered over an iron-bar-studded chunk of rockcrete, the day was lit by a terrible brightness. The sky was bleached of colour and everything before him was bathed in the blinding light of a star.

The Dies Irae was enveloped in a dazzling ball of incandescent fire, huge sprays of plasma gouting from its belly. The enemy Titan with the burning white eyes had its fist buried in its guts, tearing and destroying the magnificent daemon machine. Locked together, the two Titans wrestled to escape each other's grip, the ground heaving with their battle.

As Honsou watched, a terrible groaning rent the air as the two machines rocked past their combined centre of gravity and slowly began to fall towards them into the ditch.

'Run!' he shouted, all thought of a disciplined retreat forgotten in the face of this new danger. He sprinted past the ravelin and leapt up the rubble slopes of the ditch as the two war machines slammed into the outer face of the curtain wall between Vincare bastion and the gate. Their massive bodies scraped down its face, trailing flaming sheets of burning plasma and ripping another great tear in the walls.

Honsou scrambled over the lip of the ditch, desperate to reach the safety of the earthworks. Forrix ran alongside him, his new bionics enhancing his speed, despite the Terminator armour he wore.

The two Titans slammed into the ground, the impact throwing Honsou from his feet and hurling him forward. He smashed into the top of the earthwork, rolling over its top as a river of plasma spilled from the ruptured reactors of the Titans.

Burning plasma flooded the ditch, incinerating the corpses that filled it in an instant. The Primus Ravelin was destroyed, crushed beneath thousands of tonnes of armaplas and ceramite. Huge flames and geysers of magma-hot steam ripped along the ditch, vitrifying the rocks throughout its length.

Razor sharp chunks of white-hot debris rained down inside the citadel, one shard from the Honoris Causa's bridge section hammering through a section of ramparts less than five metres from Castellan Leonid.

Both war machines thrashed weakly in the molten soup that filled the ditch, grappling to the last as the searing fires consumed them.

The first attack had failed.