Magnus stood firm before the Titan, a child before a towering monster. He lifted his arm, palm upward, as though to offer the giant some morsel to sate its appetite. Ahriman saw a thin smile play around his primarch’s face as he drew his fingers back to make a fist.

The enormous gauntlet that had spat such venom upon Magnus was crushed utterly as an invisible force compressed it. Fire bloomed from the shattered hand, black tendrils like dead veins hanging from the rain of its shoulder as Magnus coolly crashed the entire length of its arm. The giant war machine shook, the movement unnatural and hideous in its imitation of pain. Land Raiders swept in to press the advantage, furious, rippling bolts of laser energy smacking the Titan’s legs and torso.

The second machine rotated its lance, and the air grew thin, as though the Mountain had sucked in a great breath. An impossibly bright pinpoint of light grew at the end of the weapon before a pulsing storm erupted in a blaze of streaming fire.

Three Land Raiders exploded, instantly vaporised in the blast, and a fireball of burnt metal mushroomed skyward. The surging beam of liquid light swept on, carving a glassy trench across the valley and immolating everything in its path. A group of Hathor Maat’s warriors on the periphery of the seething fire burst into flames, their armour running like melted rubber. Ahriman could hear their screams. The heat wash of their death was a rancid flesh stink that threatened to break his concentration.

“Ahzek!” cried a voice, almost lost amid the shriek of the Titans’ weapons fire. His anger fled, the rigid mental discipline of the Enumerations reasserting itself. He turned to the source of the cry, seeing Ohthere Wyrdmake frantically beckoning him from behind the cover of a spit of red rock. Gunfire streamed from the Space Wolves position.

Logic took hold, the measured calm of mental acuity honed over a century of study.

“Uthizzar,” he said, “let’s go.”

Uthizzar nodded and together they ran through the deafening, blazing crescendo of weapons fire that filled the valley. Firepower to end entire regiments surged back and forth: heatwash, ricochets and shrieking intakes of breath from guns capable of mass murder. The shape of the battle was fluid and its tempo was increasing.

The Astartes were fighting back, filling the valley with disciplined volleys, but save for the augmented fire of Khalophis’ warriors, it was having little effect. There were too many targets for the Titans to effectively engage them all, but that wouldn’t last long. Fifty more Astartes died as the second Titan’s fist spat a shrieking hail of death, the impacts sounding like a thousand mirrors shattering at once.

Ahriman ducked into cover with Uthizzar, feeling strange at taking refuge with warriors in midnight-grey armour instead of crimson and ivory. A shaggy wolf snapped its jaws at him, thick saliva drooling between its fangs.

“What were you doing out there?” shouted Wyrdmake over the din of gunfire.

“Nothing,” replied Ahriman, unwilling to speak of the mental ordeal he and Uthizzar had endured, “just picking our moment to run for cover.”

“What I would not give for a Mechanicum engine right now,” hissed Wyrdmake as a rolling wall of boiling air washed over their position. The Rune Priest’s staff crackled with miniature lightning bolts. The power filling the valley had almost overwhelmed Ahriman with the urge to wield it, but Wyrdmake appeared oblivious to its temptations.

Space Wolves shouldered missile launchers, sighting on the undamaged Titan. Skarssen shouted an order, lost in the din, pointing towards the Titan’s head. Spiralling contrails zoomed upwards, detonating against the surface of the giant’s head, rocking it back, but doing little obvious damage.

“Again!” shouted Skarssen.

“That won’t bring it down!” cried Ahriman over the booming cough of missile fire.

“Never hunted a Fenrisian Kraken, have you?” cried Skarssen.

“How perceptive,” snapped Ahriman, ducking down as the rocks around him exploded in pinging fragments. A Space Wolf went down, but picked himself back up again. “What has that got do with anything?”

“A single wolfship will be smashed to kindling and its crew devoured,” said the Wolf Lord, as though enjoying this fight immensely, “but put a dozen in the water and then it becomes a hunt worth undertaking. Shield scales buckle, flesh tears and blood flows, the beast weakens and then it dies. Every harpoon matters, from the first to the last.”

Then all thought was obliterated as a world-shaking scream of ancient loss and pain ripped through the mind of every warrior.

IT WAS THE sound of worlds ending. It was the birth shout of a vile and terrible god, and the death scream of glory that died when the race of Man was young. Ahriman collapsed as pain like nothing he had ever known wracked his body with a torturer’s skill, finding the secret parts of him and driving itself home without mercy. His fragile control crumbled in the face of it, his mind ablaze with images of a civilisation overturned, worlds consumed and an empire that had spanned the stars brought low by its own weakness.

No one was spared the scream’s violence, not the Space Wolves and certainly not the Thousand Sons, who suffered worst of all. The pain drove Ahriman to the edge of sanity in the blink of an eye.

Then it was over. The echoes of the scream retreated, its power like a breaker upon a seawall, forceful and spectacular, but quick to fade. Ahriman blinked away tears of pain, surprised to find he was lying flat on his back.

“What in the name of the Great Wolf was that?” demanded Skarssen, towering over him as though nothing had happened. Once again, Ahriman was impressed by the Space Wolves.

“I’m not sure,” he gasped, blinding spots of light sparkling behind his eyes from burst blood vessels, “a psychic scream of some sort.”

“Can you block it?” asked Skarssen, holding his hand out to Ahriman.

“No, it’s too powerful.”

“We will not need to,” said Uthizzar.

Ahriman took Skarssen’s hand and hauled himself upright, his head still aching from the pressure of the unexpected war shout. Uthizzar nodded at him and pointed out into the valley.

He glanced over the white-hot rocks he and the Space Wolves sheltered behind. The searing fire of the Titan’s weapons had vitrified them, the solid stone now smooth and translucent. Razor-edged discs the width of a man were embedded in the glass, caught by the molten rock before it hardened and singing with the vibration of their impacts.

Blinking away bright afterimages, Ahriman looked down the valley. The elongated head sections of the war machines were burned black, their previously impervious armour cracked and their bejewelled heads split open. Ahriman smelled the burnt metal taste of an incredibly powerful aetheric discharge. Whips of wild lightning lashed from the broken armour, and he watched with fierce pride as Magnus the Red stalked through the storm of fire and death towards the towering machines with twin fists of fire.

Ghostly light rippled across the Titans. Explosions bit chunks out of their ceramic skin, and viscous black liquid, like boiling oil, slithered from the wounds.

“You see!” roared Skarssen. “They bleed!”

“It won’t be nearly enough,” returned Ahriman, “no matter how many harpoons you bring to bear!”

“Just watch,” promised Skarssen, throwing himself flat as a shrieking wall of light broke against their cover. Superheated air hissed and greedily sucked oxygen from the air with a thunderclap.

“The Storm breaks!” roared Wyrdmake. “The Tempest gives its sign!”

Magnus faced the giant machines alone, his feathered cloak spread behind him like an eagle’s wings. His flesh swelled with power, and for a brief moment it seemed that he matched the Titan in stature. His unbound hair was a stiffened mane of red, and his limbs ran with electric light. The Primarch of the Thousand Sons drew back his arm and loosed a stream of blue fire that struck the nearest Titan square in the chest.