Both princeps grumbled their assent and Sharaq shut down the link between them as the Warhounds loped off into the wind-whipped ash and dust.

Dalia raced from the control room, chased by screaming alarm bells and the blinding light of the Astronomican. Howling cants of binary squealed and the air foamed with torrents of panicked data streams.

Tears spilled down her cheeks as she heard the agonised screaming of Jonas Milus, the sound echoing from the front of her skull to the innermost reaches of her psyche. Dalia had promised herself that he would be safe, that her work would not see him killed in the name of scientific progress.

That promise had been reduced to ashes and she couldn't bear the sound of his screams. She passed into the towering shaft chamber that rose up to the Magma City, seeing that the low archway in the silver wall was now filled with a great bronze gate. She ran towards it, molten light spilling through a circular window in its centre.

'No!' she cried. 'No! He's dying!'

She beat her fists on the metal door, bruising the flesh of her hands and drawing blood where she clawed at the glass with her fingernails. Dalia pressed her face to the window, straining to see anything through the dazzling brightness that filled the chamber and rendered what was happening within invisible.

'Open the door!' screamed Dalia. 'Open the damn door! We have to stop this!'

Dalia rushed to the keypad at the side of the door and began punching in the code required to open it. She had not been made privy to the doorway's code, but had skimmed the access protocols from Zeth's noospheric aura.

Further warning alarms shrilled and a pulsating amber light began to strobe angrily.

She felt a restraining hand on her arm and angrily threw it off.

'You can't go in there!' shouted a voice at her ear: Caxton's.

'I have to!' she wailed. 'He's dying. Oh, Throne we're killing him!'

'It's not your fault,' said Caxton, drawing her arms back from the door before she could punch in the final sequence of digits and turning her away from the light streaming through the window. 'It's not your fault.'

'It is, it is,' sobbed Dalia, burying her face in Caxton's shoulder and holding him tightly, as if the force of her grip could somehow end the horror. 'We need to get in there.'

'You can't,' said Caxton. 'Not yet. You're not soul-bound!'

'I don't care! I need to get in there!'

'No! The psychic energy will kill you if you go through that door.'

'Like it's killing them!' said Dalia. 'I've got to!'

She pushed Caxton away and entered the last digits of the access sequence.

Like a rolling surge tide, the light boiled out from the chamber of the Akashic reader, and Dalia plunged into the roaring blizzard of psychic power.

Princeps Kasim felt the savage glee of Raptoria as he pushed her to flank speed. Like him, Raptoria was glad to be walking beneath the sky, unfettered and armed for war. The between times when she languished in oily ship holds, restrained by scaffolds and manacled to the deck, had been a cage for her warlike heart, a cell for an angry killer that had denied her sublime skills as a hunter.

This was her first walk since returning to Mars for repairs, and Kasim felt the urge to kill in every piston, gear and metal joint of his mount. He looked down at the golden skull and cog medallion that hung around his neck and wished that he could reach up and touch it for luck, but his hands were encased in wire-wound haptic sheaths.

Princeps Cavalerio, the Stormlord himself, had presented Kasim with the medallion, honouring him in front of the Legio as they boarded the ships for Mars after the brutal, hard-fought campaign of the Epsiloid Binary Cluster.

Six engines had been lost and many wounded, including the already battle-scarred Victorix Magna, the towering war machine of the Stormlord.

Cavalerio had brought the badly wounded engines of the Legio back to Mars, leaving the bulk of Tempestus under the command of Princeps Maximus Karania. Months of labour by the Legio artisans had seen the damaged engines repaired and brought back to their former glory.

With the refit works virtually complete the Legio was ready to transfer back to the expedition fleet, to once more extend the rightful domain of the Imperium. Kasim eagerly awaited the Legio's return to the forefront of the fighting, for Mars had changed in the years since Tempestus had led its war machines across its umber plains.

No longer was Mars united in the dream of the Great Crusade. The clan-forges and magi had fallen to petty squabbling and spiteful acts of violence, dragging the red planet into an age of suspicion and mistrust.

Even the warrior orders had changed, forming factions and isolated bands of martial strength to protect what resources they controlled. Mortis had been no exception, extending their control through the guise of protection to many of the smaller forges and more easily pressured warrior orders.

No, the sooner Tempestus could get back to the real work of the galaxy the better.

'Where are they?' he hissed, bringing his Warhound about and angling his course to intersect with that of Astrus Lux. The view from his canopy was mostly obscured by the billowing ash storm, the thick, armoured glass streaked with a dusty residue that was the bane of cogs and gears.

'Twenty kilometres, my princeps,' said Moderati Vorich. 'Signal returns growing in strength, but they keep fading in and out… as if there's some kind of interference pushing out just ahead of them.'

'Keep us steady,' warned Kasim. 'And keep a close eye on the sensoria, they'll probably have Warhound pickets as well.'

'Yes, my princeps.'

Kasim felt the power beneath him, the fiery heart of Raptoria straining at his commands and anxious for the hunt proper to begin.

'Soon,' he whispered.

Kasim was relying on hard implants and the myriad surveyor apparatus fed information to him via the MIU, data flowing directly into his cerebral cortex as streams of neurons.

So far, Raptoria was running only passive scans, the better to hide her presence in the storm. An active scan of the area would reveal more of their surroundings, but would as good as announce their presence to any undiscovered hunters.

In such conditions, a Warhound lived and killed by its stealth - as strange as the concept of such a huge machine being stealthy might appear - and Kasim trusted his instincts to keep Raptoria safe. The interference plaguing the sensoria was troubling, and he could feel Raptoria's unease in the skittishness of her controls.

All his other senses were undimmed. He could feel the nearness of princeps Lamnos's engine, the bite of the dust on Raptoria's hull, and taste the oily, ashen flavour of the wind as it howled around him.

Somewhere out in the dust was the enemy, even if they hadn't been classified as such yet, but Kasim couldn't see them or know how close they were. Such situations were a Titan driver's worst nightmare; that your enemy could be plotting a firing solution without you even knowing he was there.

Kasim knew it was only a matter of time before Mortis and Tempestus drew blood.

The words exchanged between the Stormlord and Camulos at the Council of Tharsis had as good as guaranteed it. Kasim's warrior instinct was to strike the first blow, but he would not disobey a direct order from Princeps Sharaq.

'My princeps!' called Vorich as the ground suddenly shook with a thunderous reverberation. 'Hard returns, dead ahead! Reactor blooms and void signatures!'

'Where in the name of the Machine did they come from?' demanded Kasim. 'Identify!'

'Unknown contact, but it's too big to be a Warhound.'

The vibration of the ground had already told him that this was no Warhound. Too big for a Reaver.