The Tempest Line had been breached. The sovereign territory of one of the most honourable Legios of Mars had been violated. Armed engines had blatantly marched from their fortress and come with warlike intent to another. Despite the evidence before him, Princeps Cavalerio still could not accept that Mortis wanted to exchange fire.

Why would they risk such a thing? Supporting Horus Lupercal and engaging in provocation was one thing, but daring another Legio to fire upon your engines made no sense unless there was a darker, more far-reaching scheme at work.

If battle were joined here, little would survive, and even with the Imperator, Mortis would not walk away unscathed.

Cavalerio had always suspected that Camulos was a man unsuited for command, and this confrontation seemed only to confirm his suspicions. It was madness, and Cavalerio did not want to be sucked into that madness. The factions of the Mechanicum might make war on one another, but the Titan Legions were supposed to be above such things, to hold the ideals of a united Mars and Terra above all things, even their own differences.

'My princeps,' said Moderati Kuyper. 'The Tempest Line.'

'I know,' said Cavalerio. 'Should we open fire?'

'You have a solution?'

'At this range we don't need one,' Kuyper assured him. 'That monster's so large we won't miss.'

Cavalerio nodded, sweat streaming from his brow, and his mouth dry. His heart was beating in brutal syncopation with the fiery heart of Victorix Magna, the straining power of a supernova at the engine's core burning hotter and faster than it was ever designed to. He could hear Magos Argyre's desperate supplications to the reactor's spirit and felt the anguish of the mighty engine in the numbness spreading through his limbs.

The image of the Imperator filled his senses, both through the viewscreen and through the Manifold. Data scrolled like liquid light through his mind, and he drank in the colossal feats of engineering that had gone into its construction and the utter lethality of its existence.

Its limbs were death incarnate, the grinning skull-face an abominable harbinger of destruction. The bristling weapon towers and bastions were a martial city-fortress carried on the back of an ancient god, though this burden was borne willingly and not as a punishment.

To fight such a thing would be the greatest achievement of any princeps, but it would probably also be his last.

The monster took another step, taking with it any chance that this crossing of the Tempest Line was accidental.

'Princeps Sharaq requests instructions,' called out Kuyper. 'Arcadia Fortis requests permission to fire.'

'Vulpus Rex and Astrus Lux moving into flank fire positions,' noted Palus.

'Tell them to hold positions, damn them!' shouted Cavalerio, his pulse racing like the roaring discharge of a gatling cannon. 'No one opens fire unless I give the order. Make sure that last part is especially clear, Kuyper.'

'Yes, my princeps.'

Cavalerio had the sensation of events sliding beyond his control, and he fought for breath as the fire from his loyal engine's heart poured through the virtual marrow of his body like blood from a ruptured artery.

His vision blurred, the edges of the Manifold swimming like a badly-tuned picter.

Victorix Magna was hurting, hurting badly, and Cavalerio knew he had to end this ugly confrontation soon.

But how to do that without beginning a firefight that would destroy them all…

Raptoria strained at the edges of Princeps Kasim's control, a feral, bestial thing that demanded blood and poured violent thoughts into his consciousness. Its murderous heart had tasted the enemy's presence and felt the heat of its metal skin. It wanted to kill.

Kasim looked down at the gold cog medallion he wore and focused his mind on the discipline encoded into his thoughts by the Legio Magi before beginning this walk. Clogged data from previous engagements were washed from the peripherals grafted to the frontal lobes of each crewman's brain to ensure each engagement was begun without the mental baggage of the last, but the hungry taste of battle was impossible to wash away completely.

No engine ever really forgot the hot, metallic flavour of war.

Kasim could feel his steersman's efforts to keep the aggression from Raptoria's movements and could hear the engine's hunger for battle in the thudding, roaring drumbeat of her reactor.

Raptoria wanted to fight and, damn it, so did he.

Princeps Cavalerio was holding his fire and so too must they, but it was galling to see the engines of Mortis so brazenly insulting the honour of Tempestus. To allow this art of defiance to go unpunished was a bitter pill to swallow, and he could already feel Raptoria's ire building within his skull with the malicious promise of future pain to come.

'Power up weapons,' he ordered in an effort to assuage the engine's bloodlust. 'Disengage safeties and surrender all firing authorities to me.'

By assuming all firing authorities, he was making sure that the feral heart of Raptoria didn't overwhelm the low-grade brain coding of the emplaced gun-servitors and open fire herself.

Kasim didn't want his engine to act without his control, but if a shooting war started, he was going to be ready to prosecute it to the best of his ability.

'Why isn't the Stormlord opening fire?' wondered Moderati Vorich.

'Are you in a hurry to die?' asked Kasim. 'Because that's what will happen if we let this get out of hand.'

Despite his rebuke, Kasim was wondering the same thing. Mortis had clearly breached the Tempest Line, and Cavalerio was quite within his rights to fire. As much as his heart was spoiling for a fight, Kasim knew that the odds against victory were high.

Staring into the Manifold, Kasim saw the heroic form of the Victorix Magna standing firm before the monstrous, towering might of the Imperator. Beside her stood Arcadia Fortis and Metallus Cebrenia, all three engines dwarfed by the enemy engine.

'What are you planning, Stormlord?' whispered Kasim.

The Imperator loomed on the Manifold, a glowering god of war that could destroy them all. A few more steps and it would be right on top of them.

In the cabin cockpit of Metallus Cebrenia, Princeps Sharaq was wondering the same thing as Kasim. Moderati Bannan counted the ever-increasing distance Aquila Ignis was striding into the territory of Legio Tempestus.

Increasing the angle of his view through the Manifold, Sharaq saw Victorix Magna standing proud beside him, venting hot exhaust gases and sweating lubricant from its overflows. Even without the spiking data readings, he could tell that the venerable engine was suffering.

'Come on, Indias,' he whispered. 'Hold her together a little longer.'

He transferred his view outwards, seeing the agile, snapping forms of Vulpus Rex, Astrus Lux and Raptoria darting around the edges and rear of the approaching Imperator like pack wolves hunting a stag. Ever bellicose, their weapons were powered and ready to fire.

The ground shook and Sharaq could feel the tremor through every joint of his engine's structure. Inertial dampers could compensate for most fluctuations in a Titan's surrounding environment, but the mighty tread of such a colossal enemy was beyond its power to completely dissipate.

He looked down at the far away ground, feeling a stab of pity for the massed ranks of skitarii gathered around his engine's splayed feet. To face a beast like the Imperator from a Warlord's cockpit was a terrifying enough prospect, but to stand naked before it without the protection of voids and armour…