'Is this what I think it is?' asks Hol Beloth.

Kartho nods.

He feels the warp-flask at his hip squirm with agitation. With the acquisition of this weapon of total destruction, his union with the immaterial creature grows ever closer. Kartho feels its resistance. It wants to finish its hunt, but the fates have decreed their joining and nothing will prevent it.

'We cannot fight the Ultramarines conventionally,' says Kartho. 'We are newborn Catachan Devils in a bottle, each capable of killing the other, but only at the risk of his own life.'

The Terminators level their guns at the brotherhood warriors.

'That is not how we will fight,' continues Kartho.

The dying men drop to their knees and spread their arms in gratitude. Bare bone gleams. Ribs shine wetly through sloughing flesh. A bark of gunfire tears their dissolving bodies apart in an explosion of rotten matter. Flaming lumps of meat spatter the buildings nearby.

Eriesh Kigal affixes melta-charges to the vehicle. There must be no trace of it left for the geo-sats to discover. The intense heat will vaporise the transport and kill off any traces of biological taint. The Ultramarines must have no warning of the new threat that has emerged from the weapon stores of CV427/Praxor.

'How do you intend to use it?' asks Hol Beloth.

'How do you think?' says Maloq Kartho. 'I am going to use it to kill Calth.'

XIV.

A haze of light lies over the plotting table's surface like a low-lying fog. Drifting particulates are caught in the diffuse light of the holos, causing flickering refraction errors in the topography displayed. It is Calth's surface, rendered in greens, browns and yellow. Icons representing Ultramarines positions and their allies are marked in gold and blue; known Word Bearers and cultist positions in hostile red.

Two consistent red icons are of greatest concern to Ventanus one in the heart of the foundries north of Lanshear, the other within the Uranik Radial.

'How often do the geo-sats initiate a surface augur?' asks Sydance as Tawren zooms in on each icon, friendly and hostile. Time stamps appear above each one.

The most recent is six hours old.

'Access to orbital auguries is still sporadic,' she says, shifting the map around with thought impulses through the MIU cabling plugged into the table. 'Most of the geo-sats were knocked out in the first moments of the attack. The few that remain are slaved to the orbital weapon platforms to alert us to any surface movements of Word Bearers forces.'

Ventanus repeats Sydance's question. 'How often?'

'Every ten hours,' says Tawren. 'That's as much inload as the Ultimus noosphere can accommodate until more powerful data-engines can augment its capacity.'

'That's a long time,' says Hamadri.

'A long time?' snaps Sydance, shaking his head. 'It's a lifetime. This map is worthless. Remus, we can't devise theoretical, let alone practical, from data that's ten hours old.'

'Six hours,' says Ventanus.

'It could be six or ten minutes and it would be just as bad,' says Sydance.

'The map is as accurate as circumstances allow,' responds Tawren, as the map zooms out.

'You're overlooking one thing, Lyros,' says Ventanus.

'I am? What?'

'There are more gold icons today than there were yesterday,' he says. 'Every day our forces grow. The Word Bearers can have no such expectation. Server, how many more loyalist forces have you established contact with since the last update?'

'Thirteen more underground shelters and sealed cave systems are now confirmed,' answers Tawren, and the new additions bob like eager children on the map.

'Two weeks ago we were broken and scattered, on the verge of extermination,' says Ventanus. 'Now we have co-ordination with nearly forty thousand of our Legion brothers, a quarter of a million Army and Mechanicum assets and sixteen Legio Titanicus engines. Every day brings us closer to becoming a globally unified force. The Word Bearers are alone, cut off from every hope of aid. They are fighting just to stay alive, but we fight for Calth.'

Ventanus spreads his hands to encompass the gold icons on the table.

He sees renewed hope. His words promise them a victory, but they think the war will be won in a matter of months. They think the Word Bearers will be pushed from Calth without difficulty.

They are wrong, and Ventanus needs to bring some cold reality to the table.

Using the manual controls, he highlights the area of the map that shows the two red symbols that trouble him the most. Force disposition icons and unit identifiers flicker to life as he manipulates the controls. The data is old and incomplete, but together with what he has seen with his own eyes, it is enough.

'A Word Bearers commander named Foedral Fell is building a fortress in the northern foundry districts,' he says. 'And Hol Beloth, the warlord who razed Lanshear, has regrouped beneath the Uranik Radial. Beloth seems to have adopted a holdfast position, so we can discount him for now, but we can't allow Fell to establish a secure base in the north.'

'You have a theoretical?' asks Sydance, eager to be unleashed.

'I do,' grins Ventanus. 'We march north and kill the bastard.'

XV.

The tunnels around Ingenium Subiaco are gloomy, and lit by dancing flames that he cannot see. Each passage bears the hallmarks of being naturally formed, but their dimensions are too perfect, too geometric to be anything other than artificial. The underground structures of Calth are an ingenium's idea of paradise, a realm where geology, engineering and art come together. There are few underground cavern systems he has not visited, mapped and devised great schemes for linking.

An entire underground planetary ecology: self-sustaining and self-perpetuating.

His plans are even now being put into action designs, philosophies and practical means of achieving their completion have been transmitted to most of the largest subterranean shelters for implementation.

The cavern is a glistening silver colour, suggestive of the eastern arcologies, the walls wet and dripping. Ingenium Subiaco has never feared solitude. He has found peace in the quiet times spent at a drafting slate, buried in a technical librarium or immersed in the design theory of the great thinkers of previous ages. He enjoys time spent with friends and family, but he acknowledges that he quickly reaches a point where he wishes to be alone.

Those closest to him know this about him and recognise the signs of his wandering attention and nascent irritability. They make allowances for him and Subiaco is grateful for their understanding of what he knows is a flaw in his character.

Subiaco relishes solitude and the chance to immerse himself in his work.

But this is something else entirely; he is utterly alone.

This is not just the absence of people, but the absence of the existence of other people.

Ingenium Subiaco understands with total clarity that he is the only man alive on Calth.

He does not know where he is and has no memory of coming here.

Each cave mouth is a yawning abyss, a pathway to horror or a gateway to some dreadful terror, locked away in ages past and now free to climb to the surface.

Caves and their exploration hold no terror for Subiaco. He has squirmed through the tiniest of cracks and pushed his wiry frame into some of the most inaccessible cave systems this planet has to offer, but these yawning entrances scare him more than anything.

He cannot count how many there are; every time his gaze shifts, the cavern seems to rearrange its walls and the black-limned cave mouths constrict without appearing to move. Subiaco feels hot breath exhale from the nearest cave, and backs away.

Which route leads to the surface? Do any of them?

He can see none of the cave markings etched by the earliest explorers, designed to aid the lost in finding their way back to the surface. It is as though this cave has never been trod by Calth's people. Laughter drifts from somewhere and he spins around as shadows chase one another over the walls.

Drifts of steam sigh from cracks in the floor, but there is no heat to them. In fact, the cavern is like a storage chiller. His breath mists the air and he sees crackling daggers of ice form on overhanging crags of rock.

'This isn't real,' he says, finally making the intuitive leap to realise that he's dreaming.

But Subiaco is wise enough to see that understanding this and ending it are two very different things.

Orange light seeps into the cavern, the glimmer of distant fires. Subiaco remembers a crumbling text borne to Calth from Terra itself and said to be tens of thousands of years old. Its stasis-sealed pages spoke of a place far below the ground where all the devils and evil-doers of the world would be sent upon their deaths. This was said to be a place of fire and torment. With the sky above him and the light of the sun on his face, Subiaco scoffed at such ancient superstition, but here in the darkness, his animal core quails in fear.

The deep flames are growing hotter and the walls of the cavern begin to drip, sloughing their substance as though shaped from wax and not solid rock. The entire cavern structure is disintegrating, coming undone with the speed of an unmasked lie. The walls flake and peel away like cinders in a fire, the ceiling falling in a rain of blood-soaked ash.

And behind that waxen veneer, a swaying mesh of iron lath and haphazardly constructed supports. It is a madman's structure that cannot possibly support the burden being placed upon it.

And beyond that, a howling void of utter emptiness.

No... not empty. Not empty at all.

Unimaginably huge shapes move within the void, leviathans that have outgrown the paltry scale of the word.

It horrifies Subiaco that this fragile lattice is all that stands between him and these monsters. He backs away from the nearest chain-link wall as a vast eye blinks before him. Subiaco only knows it is an eye because a pupil the size of a small moon dilates as it notices him. The structure around him trembles, and the shockwaves spread to the farthest reaches of the caves. He hears the sound of groaning steelwork and the grinding squeal of metal on metal. Something breaks over to his left and Subiaco hears the tap, tap, tap of steel claws at the iron lath. Hears it buckling and pulled apart.

Cackling laughter bubbles from somewhere that could be a thousand kilometres away or could be right behind him. Subiaco does not wait to find out and runs in what he hopes is the opposite direction. He hears the scrape of metal-sheathed bodies pushing their way through tears that are too small for their impossible forms. He hears the shrieks of their pain and the howls of their hunger. He keeps running, knowing better than to look back and see what is chasing him.

All he knows is that he has to get away.

He runs, and the sound of hundreds of polished steel blades echoes around him. They shed sparks that light the unravelling reality in strobing flashes and throw out elongated shadows of malformed limbs, distended jaws and gutting fangs.

Subiaco screams as he hears thousands more of the amorphous, bladed things beyond the lattice pushing their way into the collapsing cave structure. They will kill him if they catch him, but he fears that what will come after will be far worse.

Then, ahead, a miracle.

A great adamantium door, a towering portal that more accurately deserves and utterly owns the title of gate. It alone has resisted the dissolution of the caverns. It alone retains its solidity in the face of the corruption from beyond that unmakes all it touches. The gate is black and glossy, built from cyclopean blocks of titanic stone hewn from the depths of a lightless ocean. It is sealed at its centre by a great golden circle upon which is wrought a complex alchemical and mathematical equation.

The Clockwork Angel.

It is an ancient problem, but one that is known to Subiaco. He understands with the clarity only terror can impart that its solution will open the gate. An ornate keyboard of brass and jet sits at the centre of the great seal and his fingers make quick stabs at the black keys.

Gears spin, pins unlock and interleaved discs of gleaming metal separate as the lock disengages and the seal splits down the middle. Golden light spills through the gap between the leaves of the gate as it opens. It is cleansing and purifying, so bright that it threatens to blind him.

Subiaco shields his eyes from the radiance, feeling its welcoming heat spread over him.

Behind him, he hears the screams of the bladed beasts pursuing him. The light is lethal to them, it burns and unweaves the dark power holding their bodies. The golden light spreads, undoing the damage done to the fragile walls of reality. Its healing energy is wondrous and the corruption beyond the veil is helpless before it, driven back beyond the barriers that keep it from invading the realms of sanity and order.

The light envelops Subiaco, and he lets it...

...and his eyes open to find his wife standing above him, her face lined with fear. He sits up, and winces as a spasm of pain shoots up his spine. The cot-bed is uncomfortable, but is a great deal softer than a bedroll on the ground. He sees his daughter curled in the corner of their assigned room, her blanket pulled up around her knees. She looks at him with wide, frightened eyes.

'I was having a nightmare,' he says, letting out a shuddering breath.

'Everyone's having nightmares,' says his wife, slipping her arms around him and resting her head on his shoulder.

'I'm not surprised,' he says, looking at the walls of their quarters as though they might disintegrate at any moment and reveal the horror behind them. He listens and thinks he can hear the faint tap, tap, tap of polished steel claws.

'What was it about?' asks his wife. 'Your nightmare.'

'I don't remember,' he says.

XVI.

The Ultramarines move out in force. Fifteen hundred warriors leave Arcology X in a kilometre-long column of heavy armour. The armoured gates open onto the blue-lit wastelands and Legion strength enough to subdue a world rides out to war. Ventanus leads them, shuttered within the commander's compartment of a Shadowsword. The super-heavy's interior is not designed for post-humans, but he has found a way to press his bulk into a space designed for a mortal body.

The interior of the super-heavy smells of grease, engine oil, sweat and sickly-sweet gusts of pine-scented incense. He hears the crew chatter over the vox, but tunes it out. He does not need to hear their operational back and forth. Not yet.

Though he holds no belief in the Machine-God of Mars, Ventanus gives a curt nod to the skull-stamped cog symbol on the bulkhead beside him. Though it goes against his grain, he touches the image with his fingertips. Not for luck, but to honour the Mechanicum forces that helped bring Calth back from the brink.

Hesst, Cyramica, Uldort and the thousands of others whose names he will never know.

As if in acknowledgement of his gesture of respect, the slates around him chime with inloading data. Reels of waxy paper spit from chattering ticker-tapes, Tawren's feed from the cogitators of Arcology X. Geo-sat imagery fills the slate before him, a haze of information four hours old that bathes his cut-glass features in a ghostly ochre light.

Their attack will reach the outer edges of Foedral Fell's foundry strongpoint in around another five hours. Ventanus plans to launch his attack immediately after the geo-sats pass overhead and paint the most up-to-date picture of the tactical situation. Nearly a hundred Land Speeders with enclosed crew compartments skim the ruins before them, feeding back more immediate intelligence on the ground ahead, optimal attack vectors and revisions to the proposed route.

It is not the way Ventanus would want to launch such a vital assault, but he suspects that few engagements in the coming war will be fought in ideal circumstances.

The landscape around Ventanus is bleached of colour by the display, but even rendered in monochrome the horror of such planetary holocaust shocks him. He saw this devastation unleashed first hand. He knows how terrible it was, but to see the surface of Calth like this is a stark reminder that this is not a warzone that nature will eventually reclaim.

This is all that Calth will ever be.

Lanshear is a skeletal steel ruin, its acreage of efficient platforms and guildhalls now a blackened, shadow-haunted wasteland. Numinus fares little better, and the spaces between them are littered with the detritus of wounded strato-carriers: flattened supply crates, ruptured barrels and upended cargo containers. Most split apart on impact, spreading their contents over thousands of square kilometres of the surface. Rifles, uniforms, food packets, boots, medicae supplies and the millions of other items required by campaigning forces at war.

It is as if a dozen armies marched through and discarded everything they were carrying before vanishing. None of the scattered items can be salvaged. All are too irradiated now to be of use. The crumpled spine of the Antrodamicus groans on the plains beyond Numinus City. The starship's plated hull is buckled and holed in a thousand places. Ventanus remembers watching it fall from the sky, a sight no sane mind could have imagined. Smoke still billows from its gutted interior, weeks after it crashed into the surface like an extinction-level meteorite.

It reminds Ventanus of a great plains-dwelling leviathan brought down by rapacious predator packs. A marvel of technology that once travelled between the stars in service to the greatest vision of mankind, reduced to rusting wreckage. A mighty king of the void brought low by treachery and left to rot on the world that most likely saw its keel first laid down.

Towers stand on the horizon like broken teeth in a rotten gum, backlit by flames from the raging fires of the refinery wells. Towering drilling rigs sway, their surfaces corroding in the stellar radiation. Ventanus sees the death of a world in all directions, cities reduced to ashen deserts, proud hubs of industry shattered beyond reclamation and entire habitation rings pounded to glassy ruin.

Calth was never the most beauteous planet of Ultramar, but Ventanus has seen enough of the galaxy to know it was a handsome one. It had not the wonder of Prandium, its cities were not the architectural marvels of Konor, and its oceans were not as majestic as those of Macragge.

Yet few worlds can match the industry of its people. Every inhabitant of Ultramar is hard-working, but the people of Calth are fiercely proud of their reputation as the hardest workers in the Five Hundred Worlds. Its shipyards on the surface and in orbit constructed more warships than many dedicated forge worlds, and no vessel bearing the stamp of a Calth shipwright ever failed in combat.

All of that is gone.

Calth's people endure, but the world they fight for no longer exists.

Ventanus remembers the Calth that was.

The dead world around him is the Calth that is.

XVII.