Flashes and rippling explosions lit up the night and his enhanced sight could follow individual acts of bravery and heroism in the battle. Not only that, but he could clearly see the yellow armour of the Imperial Fists in the flickering light. To have the ancient foe here was as close to perfect synchronicity as he could have wished. He remembered fighting Dorn's warriors on the walls of the Eternity Gate on Terra, ten thousand years ago. Then they had been warriors to walk the road to hell with, but now… ?

He would soon find out. An inferno of hate burned within his heart with a passion he had all but forgotten.

He'd watched the spear of light roar from the mountains to the east of the citadel and had experienced a moment's unease as he watched the orbital torpedo climb higher and higher.

How had it been fired and where was it bound? But these questions seemed largely irrelevant now, as it had streaked into the heavens then vanished through the clouds.

Forrix returned his attention to the battle below, sneering in contempt as he saw the Imperials begin to pull back under the fury of the Iron Warriors' counterattack. He saw Honsou leading a rabble of soldiers through the battery, killing those not quick enough to make their escape, and smiled grimly.

Honsou was becoming a fearsome war-leader and Forrix knew that, given the chance, he could be amongst the greatest Warsmiths the Legion had ever seen.

The battle below was as good as over. Forrix turned away, marching past the huge number of artillery pieces he had assembled on the promontory and over the breach Honsou had fought his way across. Tomorrow they would begin firing again and the walls of the citadel would crumble.

He crossed the entrenchment on long, flat sheets of metal, stopping as a sudden premonition sent a shiver along his spine. He craned his neck upwards.

The sky was, as usual, the colour of blood, lit by reflected flashes of explosions from below.

What had made him look up?

Then he saw it.

A burning dot of light high in the sky, arcing down towards the planet at fantastic speed. Forrix's jaw hung slack as he realised the ultimate destination of the torpedo. Hot anger flooded his body as he watched molten streamers of light flare from the torpedo as it entered the lower atmosphere.

He bolted for the keep, shouting a voxed warning to the warriors inside.

'By all that is unholy, raise the keep's void shield!'

He lumbered towards the sunken blast doors that led within, casting a hurried glance over his shoulder. The burning corona of fire that surrounded the torpedo appeared to him like a baleful eye in the heavens, aimed straight for his heart.

Forrix entered the keep, hammering his fist across the door-closing mechanism and set off towards its command centre. He heard the pervasive hum of the void shield generator buried beneath the tower powering up and fervently hoped that it would raise in time.

For if it did not, he and everyone in the keep were as good as dead.

The torpedo impacted almost exactly in the centre of the Kane bastion of Tor Christo where its triple stage warhead detonated with devastating results. The lead element of the warhead was designed to crater an opening through the thick hull of a starship, while the tail element would explode simultaneously, acting as a propellant and hurling the middle charge deep within its target, But instead of the metres-thick, reinforced adamantium bulkhead of a starship, the torpedo slammed into the ground of the Kane bastion, travelling at over a thousand kilometres an hour. The first stage of the torpedo exploded with phenomenal power, flattening everything within three hundred metres and blasting a crater fifty metres deep. The tail section blew and thrust the torpedo deeper into the rock of the promontory where the more powerful centre charge detonated with the power of a sun, ripping the rock of Tor Christo apart.

Night became day as blinding light fountained from the impact. Tank-sized chunks of stone were hurled through the air like pebbles as an expanding wave of blinding smoke and dust filled the valley. The thunderclap of detonation was like the hammer of the gods, come to smite the surface of the planet, and a surging mushroom cloud billowed a thousand metres into the sky, hurling ash and burning rock in all directions.

The ramparts of the bastions either side of the torpedo's impact sagged and cracked, their rockcrete walls splitting under forces they were never designed to endure. The crater in the centre of the promontory expanded with terrifying rapidity, tonnes of rubble and artillery pieces collapsing into the fiery pit.

With a tortured groan, millions of tonnes of stone cracked and rumbled, sliding free of the slopes of the promontory, crashing down in a rocky tidal wave of destruction. The western end of the first parallel was buried beneath the avalanche of rock, and the zigzag approach saps leading to the second parallel filled and collapsed. Thousands died screaming as they were crushed beneath the sweeping tide of earth.

The battery constructed before the walls of the Vincare bastion vanished in a torrential downpour of earth and rock, the guns buried forever beneath thousands of tonnes of debris.

Hundreds of secondary explosions were touched off as burning shards of wreckage dropped into the Iron Warriors' camp, detonating ammo dumps and fuel bladders, and setting light to hundreds of tents. Anarchy filled the camp as men attempted to fight the blazes, but they were as ants fighting a forest fire; nothing could halt the spread of the voracious flames.

The blast wave buffeted the towering form of the Dies Irae, but the workers had done their job well and the towering buttresses and scaffolding held, keeping the monstrous leviathan from toppling. The massive Titan shook, its joints groaning and squealing as its external gyros fought for balance, but the Shockwave passed over it and left it intact. Several other Titans were not so fortunate and three Warlords of the Legio Mortis were brought down by massive hunks of rock or collapsed by the force of the blast.

The death toll had reached nearly ten thousand by the time the final echoes of the blast had died away and the blinding light of the torpedo's detonation had faded. All that remained of Tor Christo was the void-shielded keep, perched precariously on a splintered corbel of rock.

In a single stroke, Guardsman Hawke had suddenly tilted the balance of power on Hydra Cordatus.

Castellan Vauban pushed himself up out of the dust and earth and shook his head clear of the ringing din that filled his skull. Bright light filled the valley and he laughed in triumph as he saw the enormous mushroom cloud wreathing Tor Christo in smoke and flames.

He and Leonid had seen the torpedo launch, but they had been too busy rallying the men to fall back towards the Primus Ravelin to follow its course. The chaos of the attack on the battery had consumed him and the first he'd known of the torpedo's impact was when he'd seen his shadow suddenly thrown out before him and an enormous force smashed him to the ground. Fleeting impressions of flashing light, thunderous detonations and pain as rocks and earth came hammering down around him.

Dizzily he pushed himself to his feet, casting his gaze through the grey smoke, attempting to see the extent of the damage, but it was futile. He couldn't see more than a dozen metres: the dust and smoke was too thick. He could see shapes picking themselves slowly from the ground, but whether they were friend or foe was impossible to tell.

Muffled rallying cries of sergeants pierced the gloomy, dust-filled air and he thought he heard Leonid's voice calling his name, but it was hard to tell. He tried to shout a reply, but his mouth was dry with ash and all he could manage was a hoarse croak. He spat, wiping his face clear of dirt and futilely dusting down his jacket and breastplate.