The many ships docked on Mars’ orbital Ring of Iron unmoored and began to move into formation against the lone intruder. They quickly formed a concave wall of adamantine and iron, and even as the Mekhane remained out of their most extreme weapon ranges, the battle cogitators began forming a gestalt hive mind to enact a flury of calculations.

Torpedoes were launched in swarms, and after a while the first volleys of Nova Cannons and cannon arrays were fired, all timed precisely to bludgeon the enemy with sheer volume of explosives when it got within range. The projectiles were of such density that they registered as a solid nebula on the auspex sensorias, but the Mekhane did not slow or deviate from its course. However, when it reached the predicted point minutes later, the shells, torpedoes and exotics warheads were all shot down by a flurry of point defense fire. Beams of white laser sliced through the void to prematurely detonate or simply melt away the storm of projectiles. Nothing made it across to so much as spark off the Nexus ship’s shields.

The Mekhane retaliated promptly by vanishing from the sensor grid in one second, and materializing right in front of the wall of ships. Before the cogitators and reflex drives could process the change, the Mekhane invaded the Mechanicum’s fleet-wide network and unleashed their doom.

*****

An interesting thing about metanatural cognitohazards is that if you’re skilled enough, the physical delivery system need not be related to the metaphysical payload. An eldritch-drenched breakup song could, if done right, cause a laughing memetic infection. A child’s poem can be used to incite rabid bloodthirst in its listeners.

I found that it makes it harder for your enemies to decipher and prepare themselves. Also makes it very interesting. After all, if I’m allowed to troll away, why not, right?

Let’s see if this reality is aware of the greatest eldritch being of them all…

*****

Captain Melef Vhal was confused at first as the enemy ship blasted out seemingly harmless energy. The cables protruding from his eye sockets and wired directly to his optic nerves perceived the phenomena from the various visual receivers on his cruiser, Axe of Mars. Then he felt his ship deciphering the lingering energies, and confusion turned into horror as a dark song began to spread from the cogitator systems.

The sirensong virus spread quickly throughout the Axe of Mars, infecting servitors, thralls and tech-priests who were bound to the ship’s neural network, remotely or otherwise. Even the ship’s venerable machine spirit was forced to slough off most of its essence, leaving only a bare husk. Everything affected shut down all their functions, save for the bare minimum of power to add their voice to the song. 

“No! Sever connection! Shut it down! Abort! Abort!”

The remains of Melef’s frail mortal body struggled against his tomb-throne as the virus engulfed the bridge. His bony right arm desperately tried to yank the cables out of his eyes even as his back squirmed to be free from his throne’s spinal interface. The captain was ultimately helpless against the infection, as was the entirety of the bridge crew. In less than a second of breaking into his augmentations and infecting his artificial and biological neural pathways, the accomplished captain of the Axe of Mars was reduced to another limp, slack-jawed victim whose throat forcibly joined the choir of madness.

Thanks to the gestalt cogitation within the fleet, the sirensong virus infected the entire defensive fleet and rendered them effectively dead in the void.

Those mortals unlucky enough to be unconnected to the fleet’s network and thus were unaffected quickly realized that they were now trapped. They watched and listened in horror as all around them their comrades, the work stations and even the ship itself sang in unison. The air cyclers coughed and churned, the lights flickered, the gears and pistons rattled, all in time to the dark song that echoed through every lifeless hull.

*****

“Haachama ch- szzkkrttt…”

Fabricator-general Kelbor-Hal had acted quickly when he saw the signs of desecration. The communication servitors linked to the fleet in orbit had stuttered and twitched and the magos immediately sent a burst code to his retinue of Skitarii. The servitors melted like wax under a flurry of precise lasfire before their vocalizers could finish whatever corruptive audio overtook them.

Orbital control was clearly lost, and it seemed that there was some degree of factuality about the Nexus in the irrational information he received. But the Mechanicum were above mere virus spreads.

Through electric-fast binaric cant, Kelbor-Hal sent out his orders through Mars’ global network, relaying the rites of activation to the great forges. As the armies of the Mechanicum mustered, the fabricator-general kept track of the infidel vessel, already forming various estimates on possible invasion points. As he was aware of the Nexus’ foul objectives, the possible landing options were narrowed down to just over a thousand eligible sites. As the ship got closer, Kelbor-Hal could further narrow down the options.

For now, holy Mars was on full alert. From the lowliest of combat servitors to the god engines of the Collegia Titanicus, no resource would be spared against the heathen. Ground-to-orbit defenses were brought online for the first time in centuries, with whole covens of tech-priests speeding the rites of activation as best as they could. The Ring of Iron, the orbital dockyard belt around the planet, had all its power diverted to the weapon batteries that faced the Nexus trespasser, even if it meant burning out ancient capacitor banks and generators. 

The enemy would not be underestimated again.

Just to be safe, Kelbor-Hal enacted a strict, planetwide information quarantine; No further information about the Nexus would be harvested or studied, on pain of prompt and permanent deletion. For all intents and purposes, the invader was to be treated as an Illuminati Damnatus level cognitohazard until all traces of its trespassing were purged. 

One might be forgiven to think that it was a waste to utterly obliterate something without leaving even a scrap to study, but the heathenous knowledge that was the Nexus deserved no place in the Omnissiah’s light. Besides, if they could remove this ‘Sev’ being, the Nexus homeworld should then be open to the Mechanicum’s reprisal.

The Mechanicum, not the Imperium. 

At the very least, Kelbor-Hal was grateful to the Nexus for exposing the Emperor for the false god that he was. Now, the Cult Mechanicus was free from its oppressive shackles, veiled as an ‘alliance’, with the crude Imperium. Once this whole sordid affair was done with, the fabricator-general swore that Mars will balance the scales with its former ‘ally’, as the Omnissiah - the true Omnissiah - wills.

Kelbor-Hal’s processes suddenly underwent a system-wide flush, his diagnostics picking up the chemical imbalances in his primary brain and rectifying it with the appropriate chemical cocktails. Returning to a more appropriate state, the fabricator-general focused his attention to the enemy ship.

Against all sensible predictions, the Nexus vessel was aimed at Olympus Mons, Kelbor-Hal’s own realm. The archmagos felt himself swaying under the vice of emotion as the sheer audacity stoked his anger.

“Let it be known,” he declared through every channel his rank authorized him to, “The heathen seeks to land within the boundaries of Olympus Mons. Margin of error is within negligible bounds. The alien mechanism is a perversion of the True Path. Let all who serve the Omnissiah meet the infidel to present proof positive of the Machine God’s disdain.”

The call was answered by virtually every forge temple, every cult, every Knight House and every Titan Legio. The fury of Mars was awoken, and it all converged, united, to meet the approaching enemy.

Fabricator-general Kelbor-Hal allowed himself the weakness of feeling primal anticipation for the coming display of violence.

*****

I had the Mekhane leave the orbital dockyards alone and focus solely on the landing point. Keeping the megastructure intact might serve as a good added bonus on my end later on in negotiations, and the lasers and building-sized shells were barely registering on the shields anyway.

With the Imperium wisely keeping out of the fight, I now had a hostile world to try out more theoretical forms of warfare that were deemed too devastating back home. I wasn’t about to completely desolate the planet, of course. Even after I got what I came for here, snuffing out the Mechanicum here would be counterproductive to the Imperium’s existence as a buffer state in the long run. I just needed to break the place sufficiently and then sell the rights over to the Imperium for an adequate price.

Like say maybe more systems earmarked for Nexus control, and some one-sided agreements which included a permanent representative on Terra to keep an eye on things. Eh, I can work on that later. Post-victory conditions later, exciting cyborg crunching now.

“Surface scans show significant potential hostiles converging towards our landing site,” Mekhane helpfully informed me. “Their saturation surpassed minimum levels for orbital bombardment. Should I begin calculating firing vectors?”

I thought over that question for a bit. “Hm… Yeah, sure. Don’t fire yet, and try to get firing solutions that’ll herd the enemy in. Don’t fire yet though, not until I give the order.”

Not until the rest of the toys had some playtime at least.

“In the meantime, how’s triangulations on the orbital dockyards?”

“Signals secured and stable, Sev.”

“Great, you can begin sending over the Strigoi.”

“Affirmative. Commencing Dalek operations on artificial planetary belt.”

*****

Within the hub command of Magma City, Adept Koriel Zeth watched as data from the Ring of Iron flooded the Martian network. What began with a single intruder alarm within a generatorium sector quickly turned into a rapid spread of alerts, priority messages and telemetry updates. How the enemy managed to precisely deliver their payload deep within the megastructure baffled her; assuming it was via matter displacement, heavy interference from the sheer mass of the dockyards should have been enough to cause near-total data corruption.

Pict captures from surveillance feeds delivered stills and brief recordings of hulking metal brutes with four arms and horizontal optical slits. The much rumored Abominable Intelligences of the Nexus, surely. They swarmed out like a greenskin horde, leaving nothing in their wake. Faster than even the gene-forged soldiers of the Legiones Astartes, these metal abominations overran nearly 4% of the Iron Ring before the defenders managed to muster some form of defense.

That only gave the monsters more things to kill.

Koriel watched one particular feed of one such defensive checkpoint, guarding a sector gate, getting obliterated. The 74 Skitarii defenders barely got four volleys in before the tide of metal tore into them. She clinically noted how the invaders violently and callously separated every single augmentation of each soldier from their flesh, more often than not killing their victims instantly through the immense trauma. The unlucky ones lived long enough to be tossed aside and trampled by the glinting tide of death.

Even as the checkpoint was exterminated, the other monsters moved past to pour into the next sector. Servitors, tech-thralls and enginseers were ripped apart without the tide ever slowing down. Every second, hundreds of the Omnissiah’s faithful were lost to the claws of these Abominable Intelligence. Every second, more of the Omnissiah’s hallowed ground was being despoiled. Every second, the great fervor Koriel held for this holy defense against the infidels was eroding away, to be rewritten by a growing dread instead.

By the time 16% of the Ring of Iron was compromised, the death toll was estimated at above five hundred thousand. The defensive choke points kept spiking the number up by the hundreds, and the moment the monsters breached another hab zone the estimates would likely soar above a million. 

The fabricator-general locked down all data links between Mars and the Ring of Iron by then, and Koriel understood then that one of the planet’s great wonders was now lost to them for the time being. 

Or, if she believed the heretical code cluster in her logi-banks, its fate would ultimately be left to the mercy of the Nexus Unity. A fate that would soon be shared by the Cult Mechanicus. There was some dark sense in that straying line of thought. But her faith in her creed remained strong despite the bleak showing thus far, and Koriel Zeth continued overseeing the logistics of funneling the faithful and materiel to the predicted warfront.

She partitioned off a small section of her cogitation to keep track of the invasion countdown, as well as note down the minutiae of the enemy’s arrival. Using the moment anti-orbit weapons systems fired into the heavens as the point of reference, the results were bleak indeed.

At T-plus 661 seconds, the Nexus ship had broken into Mars’ exosphere without suffering any detectable signs of damage. Their shields were able to withstand the storm of lance and cannonfire, and even several exotic Ordinati weapons. Relic shieldbreaker warheads were exhausted to no effect, as were massive disintegrator beams and graviton shackles.

By T-plus 792 seconds, the subverted Ark Mechanicus had broken through the mesosphere and seemed intent on diving straight at the planet. The energy readings from its shields were dropping, only because 26% of the energy-based defenses had burnt out their capacitors or required urgent maintenance.

The ship reached the troposphere at T-plus 814 seconds, and the Titans and other warmachines with the ability to do so began to lend their firepower against the descending city-sized vessel. No significant change was detected to its shielding.

At T-plus 822 seconds, the Nexus ship made planetfall after quickly clearing its landing site with a scouring blast of impossibly high-powered lasweaponry. Koriel’s processing froze up for a moment as she read the energy output. Assuming all the drones and auspexes were not malfunctioning, the combined Nexus’ laser weapons were emitting enough power to be scaled to small stars. Nevermind the firing of the weapons, how the ship remained intact after such an output was a miracle in itself. After that, it was no wonder then that their shields could stay up.

What were a few focused gigajoules compared to harnessing yottajoules of energy?

Gnawing dread blossomed into a cold wash of stuttering code and the first true inability to compute. The confused binaric chatter in the battle network told Koriel that she wasn’t alone. The puzzlement and fear was enough to give even fabricator-general Kelbor-Hal pause, as most of the cohorts stopped firing.

At T-plus 826 seconds, amidst the awed confusion of the defenders, the Nexus breached all levels of the Mechanicum’s communications network to flood it with a male’s voice. “This is Sev of the Nexus Unity, addressing the Mechanicum of Mars. This is the first and only offer for you to cease hostilities and keep to the treaty signed by the Emperor of the Imperium. Comply, and no further actions will be taken by the Nexus.”

“We are not bound by the false god’s promises!” Kelbor-Hal retorted furiously. The firing resumed again.

“So be it.” A strange noise pattern filled the channels, impossible to filter out, impossible to override. There was a descending whine, followed by the unmistakable sound of marching boots. Then came the impact percussions and some sort of instrument. Music. They were playing music? 

Adept Koriel Zeth witnessed, through the linked optics of her warriors at the front lines, as the desecrated Ark Mechanicus lowered its ramps. A myriad of forms large and small descended from them.

Sev’s voice spoke over the rising background. “Straight from the Nexus Unity, the Westwood war factories proudly present…” For some reason, Koriel could imagine the excited grin of a man, one that just barely held back dark laughter. “Command and conquer, red alert.”

The cacophonous song blared loudly as the army of the Nexus poured out from the landed ship and began firing into the defenders. 

The defense of Mars began in earnest.

It was a short lived massacre.