'No,' insisted Severine, pointing with her good arm at the vast shimmering silver walls and roof. 'It's more than that. The angles and the perspective… they're… all… wrong! Look!'

As though Severine's words had unlocked some hidden aspect of the cavern, each of them cried out as the sheer impossibility of its geometry, previously concealed from their frail human senses, was suddenly and horrifyingly revealed.

Dalia blinked in confusion as a sudden wave of vertigo seized her, and she grasped Rho-mu 31's arm to steady herself. Though her eyes told her that the walls of the cavern were impossibly distant, her brain could not mesh what she was seeing and what her mind was processing.

The angles were impossible, the geometry insane. Distance was irrelevant and perspective a lie. Every rule of normality was turned upside down in an instant and the natural order of the universe was overthrown in this new, terrifying vision of distorted reality. The cavern seemed to pulse in every direction at once, compressing and contracting in unfeasible ways, moving as rock was never meant to move.

This was no cavern. Was this entire space, the walls and floor, the air and every molecule within it, part of some vast intelligence, a being or construct of ancient malice and phenomenal, primeval power? Such a thing had no name; for what use would a being that had brought entire civilisations into existence and then snuffed them out on a whim have of a name? It had been abroad in the galaxy for millions of years before humanity had been a breath in the creator's mouth, had drunk the hearts of stars and been worshipped as a god in a thousand galaxies.

It was everywhere and nowhere at once. All powerful and trapped at the same time.

The monstrous horror of its very existence threatened to shatter the walls of her mind, and in desperation, Dalia looked down at her feet in an attempt to convince herself that the laws of perspective still held true in relation to her own body. Her existence in the face of this infinite impossibility was meaningless, but she recognised that only by small victories might she hold onto her fracturing reason.

'No,' she whispered, feeling her grip on the three-dimensionality of her surroundings slipping as the distance to her feet seemed to stretch out into infinity. Her vertigo suddenly swamped her and she dropped to her knees as her vision stretched and swelled, the interior of the cavern suddenly seeming to be as vast as the universe and as compressed as a singularity within the same instant.

She felt the threads of her sanity unravelling in the face of this distorted reality, her brain unable to cope with the sensory overload it was failing to process.

A hand grasped the sleeve of her robe, and she looked into the lined, serious face of Zouche. With a gasping snap, her focus returned, as though the squat machinist was an anchor of solidity in an ocean of madness.

'Don't look at it,' advised Zouche. 'Keep focused on me!'

Dalia nodded, her senses numbed by the violated angles and utter wrongness of the cavern walls and the thing they cloaked from view. How had she not noticed it before? Had it taken her senses a moment to try to process the sheer impossibility of what she saw?

Even knowing the warped nature of what she was experiencing, she still felt dizzy and disorientated, so she followed Zouche's advice and kept her attention firmly focused on his loyal face.

She took a series of deep breaths with her eyes shut before pushing herself to her feet and turning to face Adept Semyon, who stood beside the lectern. The dark-robed adept and his towering combat servitor were an unwavering slice of reality amid the chaos of her unmade vision, and the more she concentrated on him, the more her brain forced the anarchy of angles and rogue geometry into a semblance of normality.

She could still sense the roiling power and madness behind the thin veil of reality her mind had imposed, but pushed the thought of it to the very back of her skull.

Caxton lay curled in a foetal ball on the ground, his eyes screwed shut and a thin line of foam dribbling from his mouth. Rho-mu 31 was down on one knee as though in prayer, gripping his weapon stave tightly as he fought down the maddening vision in his head.

Severine stood where Dalia remembered her, staring out over the expanse of the cavern at the furthest extent of the ledge.

'I understand,' Dalia told Semyon. 'The Dragon… I don't know what it is, but I know where it is.'

'Do you?' asked Semyon. 'Tell me.'

'This cavern… everything in it. This is it. Or at least a sliver of it.'

Semyon nodded. 'A tomb and prison all in one.'

'How?'

Semyon beckoned her over to the lectern and opened the book. 'Look. Know.'

Dalia took halting steps towards him, feeling the strange sense of inevitability that had gripped her when they had travelled on the mag-lev. She had a sudden sense that she was meant to do this, that she had been heading towards this moment all her life.

She reached the lectern and looked down at the book, its pages filled with the tightly knotted scrawl of a madman with too much to say and too little space to write it. The words made no sense to her, the language archaic, the lettering too small and compressed.

Even as she tried to tell Semyon she couldn't read his words, he reached over the book and took her hands in a grip of iron as its pages turned in a frantic blur of parchment.

'No… please…' she begged. 'I don't want it!'

'I said the same thing,' said Semyon. 'But he doesn't care what we want. We have a duty.'

Dalia felt the inhuman fire in Semyon's blood through the searing heat of his hands. The pain was excruciating, but it was nothing compared to the terror that filled her at the dreadful truths contained in the immortal depths of his eyes.

She tried to look away, but his gaze held her locked tight.

His skin blazed with a pure golden light. 'Look into my eyes and see the Dragon's doom!'

And in one awful rushing flood of knowledge, Dalia saw everything.

As Sigismund's companies landed at Mondus Occulum, the rest of the Imperial expeditionary force was fighting all across the surface of Mars. After a rapid deployment under fire in the shadow of Pavonis Mons, thirteen companies of the Saturnine Hoplites advanced on the lines of circumvallation surrounding the forge of Ipluvien Maximal.

At first, the soldiers of Saturn made good progress, their heavy armour soaking up the fire from the enemy warriors tasked with manning the rearward-facing defences, but within hours, a host of skitarii surged from the ridged landscape of the Gigas Fossae to flank them.

Hundreds died in every surge and clash of arms, nightmarishly augmented warriors tearing through the ranks of the horrified Imperial soldiers before finally being brought down. Beetle-backed servitors with spiked armour and hissing weapon arms bounded forward, unleashing rippling beams of incandescent light that shrieked like banshees and incinerated men and obliterated armoured vehicles with equal ease.

Bizarre tanks scuttled forward on spider-like legs to clamber over the wrecks of destroyed vehicles and slice through armour and flesh with every sweep of their energy-sheathed pincer arms. Within minutes, the Imperial advance was in danger of becoming a rout until a company of super-heavy tanks rolled through the centre of the Imperial lines to tear through the vile horde of the enemy with their enormous guns.

With the support of so many colossal armoured fortresses, the Saturnine forces rallied, quickly encircled the enemy counterattack and crushed it utterly. With their flanks secure, the battered and wary Imperial soldiers continued their attempt to relieve the siege of Maximal's forge.

Further south, two companies of Imperial Fists and four regiments of Jovian Grenadiers under the command of Captain Camba-Diaz made planetfall in the Mondus Gamma forge complex, but unlike Sigismund's warriors at Mondus Occulum, they were unwelcome arrivals.