Plumes of fire and towering stacks of iron rose from its mountainous southern regions, and networks of gleaming steel spread out like cracks in the ground through which fractured light spilled into the sky.

'Is that…?'

'Mars,' confirmed Rho-mu 31. 'Domain of the Mechanicum.'

Supersonic shells tore through the gaggle of servitors feeding on the dead techno-mats, obliterating one instantly and blowing the limbs from another. Three others staggered back, chunks of flesh blasted from their emaciated frames. They refused to fall, however, their damaged brains unable to comprehend how grievously the guns of Cronus's Knight had wounded them.

'All yours, Maven,' said Cronus, cutting off the stream of shells.

'So glad you left me something to do,' replied Maven.

Maven moved Equitos Bellum in behind the bloody servitors, the energised blade in his war machine's right fist reaching down and slicing through the survivors in one sweep. Old Stator finished off the stragglers with a short, perfectly controlled burst of laser fire, their wasted bodies exploding in puffs of vaporised blood and scrap metal.

Standing five times the height of the feral creatures, the three Knights towered over the battlefield, though Maven knew that to call it such was to vastly overstate the nature of the deaths they had caused.

The Knights were armoured in thick plates of plasteel and ceramite, protected by layered banks of power fields strong enough to weather the impact of a much larger engine's wrath, and armed with weapons that could kill scores at a time. The plates of their armour were a deep, midnight blue, the right shoulder of each one painted with the design of a wheel encircling a lightning bolt.

The same design was repeated on the long, cream-coloured banners hanging between the mechanised legs of all three war machines, the heraldry of the Knights of Taranis.

Maven rode in Equitos Bellum, an honourable mount with a host of battle honours earned in the earliest days of the Great Crusade. It had fought the enemies of the Imperium beneath a dozen different skies, and even marched alongside the Salamanders of Primarch Vulkan. The design of a firedrake carved into the skull-cockpit of the Knight recalled that campaign, and Maven never tired of telling the stories of that glorious ride into battle.

His studious brother-in-arms, Cronus, rode in Pax Mortis, and Old Stator commanded the august majesty of Fortis Metallum. All three war machines had earned their share of glory on the battlefields of the Imperium, marching ahead of the Titan engines, the god-machines.

The Knights of Taranis were feted among the warriors of Mars for their martial achievements, revered for their place in Martian history, and lauded for the wisdom of their commanders.

Even the mighty princeps of the Titan legions were known to seek the wise counsel of the order's masters, for Lords Verticorda and Caturix were known as leaders whose shared command blended the warrior's heart with the diplomat's cool.

'So why, in the name of the Omnissiah are we stuck out in the arse end of nowhere culling feral servitors?' he asked himself, before remembering that the Manifold-link between the Knights was still open.

'We're here because those are our orders, Maven,' said Stator. 'Do you have a problem with that?'

'No, preceptor,' replied Maven, his tone contrite. 'I just meant that it seems like such a waste of our strength. Can't Magos Maximal's Protectors perform their own culls?'

'Not as well as we can,' said Cronus, his answer sounding like it came from a training manual. Maven felt his lip curl in a sneer at his brother's sycophancy.

'Exactly, Cronus,' said Stator. 'We've been given a duty to protect this reactor complex and there is honour in duty, no matter how far beneath us it might seem.'

Maven sensed an opening and said, 'But the Knights of Taranis once marched with the Crusade. We fought alongside heroes of the Imperium, and now all we do is shoot feral servitors that come up out of the pallidus. There's no glory in this work.'

'These days the threats to the Warmaster's campaigns require forces stronger than us,' said Stator, but Maven could sense the bitterness beneath his words. 'The Great Crusade is almost over.'

'And what will be left for us?' demanded Maven, emboldened by Stator's words. 'There must be expeditions that need the skills of our order.'

'The expeditions do not ask for Knights,' said Stator. 'They ask for the god-machines to walk with their armies. Our role is to protect Mars and maintain the traditions of our order, and part of that tradition is honouring our obligations. Is that understood, Maven?'

'Yes, preceptor,' said Maven.

'Now let's finish this sweep and make sure there are no more of them. Maximal needs this facility kept safe, and Lord Caturix swore that we would do so.'

Maven sighed and walked his Knight to where humming power cables jutted from the hard, orange earth and spat sparks where the servitors had dug at them to feed the machine parts of their ravaged bodies. The corpses of the techno-mats and artificers sent to fix the damage lay in pools of blood that were already congealing in the heat that bled from the fusion reactor further back in the gorge.

'Check for more of them out there, Cronus,' ordered Stator. 'They usually hunt in bigger packs than this.'

'Yes, preceptor,' replied Cronus, marching his Knight past the dead servitors and through the gap torn in the barbed, chain-link fence that surrounded the reactor. Cronus guided his machine up the rocky slopes to check the ground behind an outcrop of boulders. To manoeuvre so large a machine as a Knight over such rough terrain was no mean feat, and Maven was forced to admire his brother's skill as a pilot.

Fortis Metallum's upper body swivelled around on its gimbal waist mount to face Maven, and though he couldn't see his preceptor's face through the red visor of the cockpit, he could feel the stern, unflinching gaze through the softly glowing slits.

'Keep an eye on our rear in case any slipped past us,' ordered Stator, his voice once again as grim and inflexible as the posture of his machine. 'I'll hold you responsible if they have.'

'Yes, preceptor,' replied Maven. 'I'm on it.'

It was a Martian truism that if a warrior and machine spent enough time linked together they would begin to take on aspects of the other's character. Fortis Metallum was an old machine, cantankerous, flinty and utterly without mercy.

It was the perfect match for Stator.

Maven had met countless Titan drivers and it was easy to tell which machines they commanded within moments of talking to them.

Warhound drivers were belligerent, wolf-like daredevils, whereas the men who fought from the towering Battle Titans were arrogant and ego-driven warriors, who often appeared to hold those around them in contempt.

Maven knew that such conceit was forgivable, for marching to war so high above the battlefield and unleashing such awesome destructive power would naturally swell a man's ego, but it was also a necessary defence against the engine's character overwhelming that of its commander.

Maven walked his machine backwards in a bravura display of skill, watching as Stator turned away to follow Cronus through the mangled remains of the security fencing.

A Knight was much smaller than a Titan, but the mechanics in its construction and operation were no less incredible. A Titan had a crew to maintain its systems: a servitor to man each weapon system, a steersman to drive it, a tech-priest to minister to its bellicose heart, a moderati to run the crew and a princeps to command it.

A Knight was the perfect meld of flesh and steel, a mighty war machine at the command of a single pilot, a warrior who had the confidence to wield its power and the humility to know that, despite that power, he was not invincible.