Schism of Mars

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Dark Mechanicum

Schism of Mars Battlefield Mars Conflict Horus Heresy Date 005-006.M31 Location Mars Outcome Traitor victory, Mars blockaded from 006-015.M31[2] Combatants Martian Mechanicum Imperium New Mechanicum Commanders Fabricator-Locum Kane Adept Koriel Zeth (KIA) Adept Ipluvien Maximal (KIA) First Captain Sigismund Captain Camba-Diaz Marshal Serban Oachar[4a] Legate-Marshal Mera Devallis[4a] Princeps Indias Cavalerio (KIA) Lord Commander Taymon Verticorda (KIA) Shield Captain Morvae Arcas[4a] Fabricator-General Kelbor-Hal Adept Urtzi Malevolus Adept Lukas Chrom Adept Regulus Ambassador Melgator (KIA) Princeps Camulos (KIA) Strength Mechanicum Protectors Skitarii Various Titan Legions (Legio Tempestus, Deathbolts, and others) Knights of Taranis Imperial Fists (4 Companies) Saturnyne Rams (13 Companies) Jovian Grenadiers (4 Regiments) Crimson Nova 32 Custodian Guard[4a] Mutated Protectors Mutated Traitor Skitarii Servitors Various Titan Legions (Legio Mortis, Death Stalkers, Legio Magna, Burning Stars, and others) Various non-standard war machines (Ordinati and others) Robots The Kaban Machine (KIA) Alpha Legion elements[4a] Traitorous Iron Hands[7] Casualties Significant; field abandoned Significant

The Schism of Mars is the name given to the civil war that erupted on Mars during the early stages of the Horus Heresy. The schism involved all Martian forces, civil and military, from lowly menial through Knight and Titan orders right up to the most senior Mechanicum personnel, as well as drawing in Space Marines and units of the Imperial Army.^[1e]

History

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Mechanicum (Novel)

Prelude

The Martian Schism originated in a climate of discontent; relations between various Magi were in a condition of tension, with outbreaks of violence and espionage leading to even the Titan Legions being suspected of secretly taking sides in potential hostilities^[1a]. For years, factions on Mars had bitterly argued over the nature of the Omnissiah, with many believing the Emperor to be its avatar. However a large faction led by Fabricator-General Kelbor-Hal maintained the Emperor a false idol and the manifestation of the Omnissiah had yet to arrive. More importantly, Kelbor-Hal harbored great resentment to Emperor for his conversion of Mars into an arms factory for the Great Crusade and his ban on certain types of technological research (such as artificial intelligence).^[1] Into this situation came Regulus, Mechanicum representative to Warmaster Horus.^[1e] By this point in history, the Warmaster had already settled upon his course of rebellion and had secretly gained the tentative support of the Mechanicum through Regulus and his connection to Kelbor-Hal, the Fabricator-General. Regulus' visit to Mars at this juncture was to demonstrate the commitment of Horus to the alliance with the Mechanicum and the advantages to siding with the Warmaster against Imperial rule. As a result of the information provided by Horus and carried by Regulus, Kelbor-Hal was able to open a long-sequestered area of Mars known as the Vaults of Moravec.^[1b]

The Vaults of Moravec were a repository of forbidden knowledge, ordered sealed by the Emperor himself. It soon became clear that the information and industry stored within the Vaults were corrupted by the influence of Chaos. With the opening of the Vaults, this corruption spread across Mars in a peculiarly literal way; as scrapcode. This viral information infection managed to penetrate systems and facilities all across the Martian industrial landscape, causing literal chaos wherever it struck. As a result of the scrapcode infestation, communication across and off-planet was severely disrupted and many essential industries sabotaged. A period of general confusion followed, which the Fabricator-General and his allies used to marshal their forces, intent on making sure the whole of Mars was firmly under their rule. This proved to be somewhat more troublesome than they had anticipated. Several areas of Mars remained relatively uninfected by scrapcode, insulated against the assault by their early adoption of a new, far more secure information network; the noosphere. Three of these areas were the Forges of Koriel Zeth, Ipluvien Maximal, and Fabricator-Locum Kane, who would go on to become the leaders of those resisting sublimation into Kelbor-Hal's new Dark Mechanicum.^[1e]

The Death of Innocence

While the opening shots had already been fired when the Kaban Machine of Lukas Chrom destroyed a reactor complex belonging to loyalist Adept Ipluvien Maximal, it still took a short while before open civil war began. Requiring at least a pretense to march to war, Kelbor-Hal and his allies attempted to provoke those unwilling to join them, employing various acts of sabotage, assassination and outright aggression - as when the Dark Mechanicum-aligned Legio Mortis attempted to goad Legio Tempestus into opening fire first by entering Tempestus territory and refusing to answer hails.^[1c]

Eventually the pretence Kelbor-Hal required was given to him by Koriel Zeth, Mistress of the Magma City, when she declared non-belief in the Machine God (while this was her belief, she was still loyal to Terra). The Dark Mechanicum went to war against the Magma City, bringing war to Mars as those pledged to Kelbor-Hal and Horus attacked those pledged to Terra and the Emperor. The Magna Legion assaulted the Noachis region and reduced its libraries and forges to slag. North in the Arabian region, High Magos Ahotep's forge-city in the Cassini crater was struck by a hundred nuclear missiles launched from traitor silos. Along the Lunae Palus and Arcadia regions, the Death Stalkers assaulted the fortress of Maxen Vledig's Deathbolts. Caught by surprise, the Deathbolts lost 19 Titans in the first hour and withdrew to Mare Boreum where they were quickly besieged. At the Athabasca Valles the Legio Ignatum and Burning Stars fought to a stalemate in bloody close-ranged combat. Kelbor-Hal himself soon unleashed his twisted Skitarii and Combat Servitors on the Forges of Ipluvien Maximal. Maximal was able to repel the first wave of attackers, but within hours he was totally besieged by Ordinatus engines. At the Herschel impact basin of the Mare Tyrrhenum, 900,000 Skitarii and Protectors clashed in a bloody melee that continued until nearly all were dead.^[1]

The single greatest loss of life of the war took place at the Ismenius Lacus forge-city after Dark Mechanicum forces unleashed Virus Bombs, killing 14 million within minutes. The apocalyptic conflict was not limited to the surface of Mars, and high above in the planet's orbital shipyards traitor ships exchanged fire with their loyalist counterparts after forcing Battlefleet Solar to withdraw. The Mechanicum Glorian was destroyed by Dark Mechanicum Frigates and crashed into the Basilica of the Blessed Algorithm on Mars itself. The crash annihilated millions of square kilometres and killed billions across the planet.^[1]

While conflict erupted all over the red planet, the Magma City soon became the focal point for the resistance, with both Legio Tempestus and the Knights of Taranis coming to Zeth's aid. Holding against the chaotic power of the Dark Mechanicum was a difficult business and soon not only Zeth's forge, but those of Maximal and even Kane found themselves becoming effectively surrounded by enemies and besieged. A vicious battle erupted at Magma City, led by the Legio Mortis and the Imperator Titan Aquila Ignis. However the Legio attack on Magma City was blunted when lava overran the traitor ranks, and most of the Titans of the Legio Mortis (including the Aquila Ignis) were destroyed by the Legio Tempestus. But despite the victory at Magma City, the situation remained dire for the outnumbered and outgunned loyalist forces across the planet.^[1e]

Dorn Intervenes

Twin beacons of hope for those still loyal to the Terran-Martian alliance appeared when two Imperial assault forces made up of Imperial Fists Astartes and Imperial Army formations drawn from the Solar levies under the commands of Captains Sigismund and Camba-Diaz arrived on Mars^[1d], intending to secure the two main forge-complexes which supplied Astartes arms and equipment, that of Kane and that of Lukas Chrom. The expedition also included a small force of 32 Custodes under Shield Captain Morvae Arcas. The incoming Imperial force faced no resistance from Mars' orbital defences due to the ruin and chaos befalling the Red Planet.^[4a]

Sigismund's first action was to launch a landing operation at Fabricator-Locum Kane's Forge-City of Mondus Occulum with two companies of mostly Terminators. Camba-Diaz made his own landing shortly after at Mondus Gamma, coming under immediate fire from Lukas Chrom's forces, taking heavy losses to traitor anti-aircraft fire. Camba-Diaz diverted to Solis Planum as the Saturnyne Rams landed at the ruined Forge of Ipluvien Maximal.^[4a]

As Sigismund was welcomed into Mondus Occulum by Kane, Camba Diaz returned to the fight on the opposite side of the Noctis Labyrinth at Mondus Gamma. Launching an assault led by Breacher Squads to advance to the walls, the Imperial Fists then unleashed heavy weapons to silence Mondus Gamma's anti-aircraft guns. Mere moments after these guns had been silenced, an enormous Drop Pod wave landed across Mondus Gamma, disgorging a full company's worth of warriors which pushed aside defending Tech-Thralls and Automata. The cramped wall interiors gave the Space Marines an advantage over even larger Thanatar and Domitar robots, and after the loyalists captured the automata command rely with a Vindicator assault these constructs were removed as a threat. Within the span of a few short hours, Camba Diaz had seized control of the eastern districts of Mondus Gamma and the Traitor Mechanicum was sent reeling. To reinforce his position, the Imperial Fists captain landed in Jovian Grenadiers.^[4a]

At Mondus Occulum, Sigismund held a war council with Kane as the outer reaches of the Forge-City were under attack by the Traitors. Sigismund himself then sallied forth to the outer refineries at a host of a hundred Space Marines as well as allied Tech-Thralls, but this attack was foiled in the face of Alpha Legion troops equipped with Nemesis Bolters. The full treachery of the Alpha Legion at Isstvan V had not yet transpired, compounding their confusion. Incensed that fellow Space Marines would take up arms against the Emperor, Sigismund led a furious charge that may have seen him slain by Alpha Legion snipers had allied Thallax not arrived. Pinned between two foes, the Alpha Legion was forced to withdraw. By this point, Kane had largely finished mobilizing the bulk of his army within Mondus Occulum.^[4a]

Meanwhile at Mondus Gamma, Camba-Diaz had made progress but had lost some 10% of his troops. He would not continue to try and advance until reinforcements in the form of 40,000 Jovian Grenadiers had fully landed. However their large landing craft were vulnerable to nearby traitor guns, forcing them to land outside its walls and march to their destination. The Space Marines would have to hold alone until they arrived, and to disrupt enemy movements in the meantime Camba Diaz deployed Seeker Squads. Taking up Mastodon transports that had once belonged to the Sons of Horus, Camba Diaz and 50 Seekers were able to slaughter enemy Tech-Thralls at Transit-Junction 993G. They then held their position for half an hour against a counterattack by Castellax and Vorax robots. In the ensuing battle, Diaz himself was wounded by a Plasma Mortar. But they had bought enough time to rig the highway with Melta Bombs, destroying the transit-junction and crippling enemy armour. However some 24 Imperial Fists, including a Centurion, had been forced to sacrifice themselves in this action.^[4a] Shortly after, Camba Diaz's force was assailed by a new breed of corrupted robots fuelled by warp sorcery and artificial intelligence. Nearly succumbing to an ambush by these new intelligent foes, Camba Diaz led the surviving Imperial Fists in a breakout with heavy losses. By the time he made it back to his holdings in the eastern district, he had only 50 troops remaining.^[4b]

Had it not been for the Jovian Grenadiers, the Imperial Fists would certainly have perished against the new mechanical monstrosities unleashed by Chrom. But thousands of unaugmented Humans rushed to the defence of their allies, allowing the combined loyalist force to resist the attack with heavy casualties. A bloody stalemate soon broke out in Mundus Gamma. Diaz realized they could never capture the city, and only now hoped to retrieve key assets before evacuating.^[4b]

At Mondus Occulum, Kane's Taghmata army had now fully roused for war as Traitor Mechanicum thralls launched waves of suicidal attacks against the city walls. During the entire battle the Forges of Mondus Occulum never ceased, bringing further munitions and weapons to the Legiones Astartes. Sigismund, attempting to hunt the Alpha Legion, arrived in the western edge of the city defences to find it in chaos as Traitor Tech-Thralls and Vorax Robots made a major push. Massively outnumbered, Sigismund and his Marines inflicted grievous losses upon the foe but were overcome by sheer numbers. The Alpha Legion meanwhile had used the battle as cover to infiltrate into the city interior. Pinned down, the Imperial Fists were forced to finally abandon the western defensive perimeter once traitor Titans of the Legio Mortis arrived.^[4b]

Imperial Evacuation

Faced with the firepower of incoming Titans, Sigismund was forced to withdraw as Kane loaded state-of-the-art wargear (including Mk.VII Armour) onto waiting shuttles. The warriors waged a delaying action as Mondus Occulum was razed around them. The loyalists managed to lay a number of ambushes, taking down smaller Titans and accompanying Knights and Automata. Kane and his accompanying Magi were quickly evacuated to Terra and without guidance, the last remaining loyal Automata threw themselves forward in a suicidal assault as Sigismund and the Imperial Fists withdrew. The Imperial Fists First Captain personally oversaw the destruction of Mondus Occulum's data-fane to ensure Mk.VII Armour templates did not fall into enemy hands. However this was too late, for the Alpha Legion had already acquired the plans. The commanding Alpha Legion Praetor mockingly revealed such to Sigismund over the Vox. As the last loyalists fled Mondus Occulum the city was razed to the ground by the Legio Mortis.^[4b]

Meanwhile at Mondus Gamma, a similar situation was unfolding as Camba Diaz sought to secure what technology he could before evacuating. Faced with a difficult choice, Camba Diaz ultimately chose the most strategically rational choice. He ordered his Imperial Fists withdraw as the Jovian Grenadiers stay behind to cover them, dooming them to slaughter but allowing the Imperials to escape with their best warriors and technological assets. The Jovian Grenadiers made no plea for their lives as Traitor robots and tech-thralls fell upon them, but rather played an ancient funeral dirge from Jupiter over their own Vox. Just as Camba Diaz was about to board his shuttle, he noticed that the Custodians under Shield-Captain Arcas had teleported to the battlefield. The Custodians were able to hold back the traitors long enough for the Solar Auxilia to withdraw. The surviving Custodes were able to teleport back to their own ships once their deed was done.^[4b]

The other leaders of the resistance, as well as that part of Legio Tempestus on Mars and nearly all of the Knights of Taranis, eventually died fighting the pernicious and relentless assaults of the Dark Mechanicum, leaving all of Mars effectively under the influence of Horus.^[1e]

While the Imperial expedition to Mars had suffered grievous losses and were forced to flee back to Terra, they managed to take with them a number of useful technological artefacts and experts. Foremost amongst these was the template for Mk.VII Power Armour as well as the core surviving loyalist Mechanicum leadership under Kane.^[4b]

In the aftermath of the Imperial evacuation, Imperial forces from Terra blockaded the planet, leading to several attempts by the Traitors of Mars to breakout. Prioritizing the defence of Terra, Dorn lacked the forces for the costly campaign to reclaim Mars. Thus was the containment of Mars was overseen by Imperial Fists commander Efried.^[3]

Raid on Phobos

Shortly after the opening salvoes of the war, loyalist Skitarii raided the Mechanicum tech-vaults on Mars' moon of Phobos, ensuring that the precious artifacts within would not fall into the hands of the traitors.^[8a]

Though Phobos' automated defenses were able to swiftly destroy most of the incoming Loyalist ships, Skitarii of Conclave Incursus-Lambda-Psi managed to land some 3,000 Battle-Pilgryms onto its surface. Swiftly brushing aside enemy Tech-Thralls, they then attempted to both advance and consolidate their beachhead, coming under swift assault from Servitors and Automata. Within only a few minutes, they were able to capture Auxiliary Gate 14 and access the subterranean vaults of Phobos. Moving directly towards the central vault, destroying everything they came across along the way to deny it to the Traitors. Soon enough they came across Vault 19-C, a kilometer below the surface, but here they came against enemy Skitarii from Conclave Vigilus-Alpha-Omega. The loyalist Skitarii demanded their traitorous kin step aside, in the name of rightful Fabricator-General Zagreus Kane. The Traitors dismissed this, proclaiming Kelbor-Hal as still the true Fabricator-General. At an impasse, battle erupted after only 8.2 seconds of debate as Skitarii fought Skitarii for the first time in history.^[8c]

The Traitors had the superior numbers, and so immediately rushed against the Loyalists in a headlong assault. In vicious close-quarters combat, the warriors of Incursus were eventually reduced to a small pocket fighting against a sea of foes. As Incursus fought to the last breath, they were offered no terms of surrender and wiped out by the Traitors, who even executed their wounded.^[8c]

However, the loyalists had merely used their primary force as a distraction. As the loyal Skitarii gave their lives, a smaller stealth force infiltrated the vault via an ancient tertiary entrance. Inside they retrieved what they had been ordered to retrieve: The Sarcophagus of the First Fabricator-General. After acquiring the relic they retreated back to their ships and fled Phobos for Terra to present Kane with their prize.^[8c]

The Battle for Vault Tharsis Deca-Nine

As the opening shots of the Schism of Mars were unleashed, two Imperial Fists Thunderhawk under Camba Diaz attempted to land at Vault Tharsis Deca-Nine, intent on denying the Traitors the relics within. However, they were met with a hail of traitor anti-aircraft fire and shot down over Icaria Planum, near the Noctis Labyrinth. Meanwhile, 600 Traitor Skitarii of Conclave Speculor-Gamma-Mu and a Bonepicker Host under a Skitarii Marshal Speculor/4/19/Σ/Tharsis advanced towards Vault with orders from Kelbor-Hal to secure the relics for themselves. They were met by defending loyalist Automata and a vicious battle began as the Bonepickers were quickly annihilated.^[8b]

Traitor Karacnos tanks were able to destroy many of the Castellax Class Robots, allowing the Skitarii to continue their advance and reached the vault portal. However as they used their code-engrams to unseal the vault, Marshal Speculor/4/19/Σ/Tharsis was immediately killed by a Vigilator as the surviving Imperial Fists arrived, plunging into the Traitor Skitarii with Assault Squads. A group of Traitor Skitarii immediately spent their lives to hold off the Imperial Fists as the rest of their forces withdrew. As the Imperial Fists fortified the entrance of the vault to defend it for themselves, the Skitarii surprisingly held back from an immediately counterattack. Instead, they immediately appointed a new Marshal, Speculor/4/11/Θ/Tharsis and sought to regroup and prepare.^[8b]

The new Marshal then launched the remaining 400 Skitarii of their Conclave towards the Imperial Fists barricades, running into a heavy of Heavy Bolter fire. The defending Imperial Fists were commanded by Vigilator Talar, who alongside a force of Reconnaissance Marines reaped a heavy toll on the Skitarii with their Sniper Rifles. However their enhanced endurance and sheer numbers allowed them to weather the hail of incoming fire and get close enough to the Imperial Fists to unleash their Voltlock Arquebus' before engaging them in vicious close-quarters combat. Using the bulk of their force to pin down the Imperial Fists, Marshal Speculor/4/11/Θ/Tharsis took her vanguard and targeted the Astartes snipers, which proved far easier prey. The Marshal personally slew Vigilator Talar as the Imperial Fists Snipers were massacred. The Skitarii then immediately withdrew, their task completed.^[8b]

With their supporting fire lost, the Imperial Fists then withdrew to the Vault gatehouse to make their final stand as the Skitarii regrouped and advanced once more. Using their injured in the first wave to absorb the loyalist fire, the Imperial Fists blew through most of their ammunition to destroy this fodder. The remaining loyal Astartes were then slaughtered in vicious melee combat as Marshal Speculor/4/11/Θ/Tharsis finally secured the relic they had been ordered to retrieve: a glistening metallic hexagonal device. However as the Skitarii began to withdraw, they were caught in a massive blast of explosives the Imperial Fists had set to detonate before their demise. The blast was such that it collapsed the entire Vault around the Skitarii, denying Kelbor-Hal his prize.^[8b]

The Perditum Incursion

Perditum Incursion Conflict Horus Heresy Date 007.M31 Location Mars Outcome Loyalist withdrawal Combatants Imperium New Mechanicum Commanders Primarch Corvus Corax Commander Agapito Nev Moritat-Prime Kaedes Nex Shield Captain Morvae Arcas First Ordinal Theta Gao (MIA) Lukas Chrom (WIA) Strength 900 Raven Guard 96 Custodes 340 Skitarii Many thousands of Tech-Thralls, Mutants, Cyborgs, Daemon Engines, and Automata Casualties Hundreds of Raven Guard Dozens of Custodes Nearly all Skitarii Significant

By 007.M31, Mars was completely under traitor control and Kelbor-Hal's new regime conducted purges against suspected remaining loyalist elements. Amongst those imprisoned by the traitors was the famed gene-wright Kephram Unguor. Unguor was said to have been forced to work on some new dark project which included genetic samples from fallen Custodian Guard. When an intelligence report detailing this was given to Malcador the Sigillite and Constantin Valdor, the two feared that this may lead to a bioweapon targeting the Emperor's guardians. As such, they immediately ordered an operation be launched to retrieve or eliminate Unguor, who was behind held at the Martian Perditum Incendor complex.^[4b]

It was at this same time that the Battle Barge Avenger arrived in the Sol System, carrying Corax and surviving Raven Guard from the Drop Site Massacre. After meeting with the Emperor personally and retrieving His genetic lore to build new warriors, Corax and his forces boarded the Avenger once more and set a course for Deliverance. However before leaving, Malcador was able to convince Corax to first lend aid to the coming covert operation on Mars. Thus when the Avenger and accompanying Custodes cruiser Sojourn left Terra and reached Deimos ostensibly for refit before departing, they quietly launched their own wave of over 100 Drop Pods and Kharybdis Assault Claws towards the Ring of Iron, the orbital construction and defense yard which encompassed the Red Planet. Cautious for further losses and betrayal, Corax did not commit himself or the majority of his remaining Legion to a direct invasion of Mars. Instead, he would oversee a more subtle operation.^[4b]

With the Ring of Iron devastated by the opening salvoes of the Schism of Mars, the Raven Guard were able to land on a broken fragment unnoticed and relatively unopposed. Only swarms of dormant Scyllax Guardian robots responded, and these were quickly swept aside by the Space Marines. The Raven Guard troops were amongst the most bloodied veterans remaining and included Mor Deythan, Seeker Squads, and Assault Squads. These were led by a vengeful Corax personally, who easily decimated what little resistance was encountered. The Raven Guard and a second Custodian strikeforce under Shield Captain Arcas rendezvoused at one of the fragments colossal planetward docking arms. The two forces set about laying a series of Melta Bombs and seismic charges. The Imperials set off their charges and the detached docking arm fell into Mars' gravity well.^[4c]

The docking arm fell through Mars' thin atmosphere, colliding just south of the Solis Planum. It spread a cloud of destruction and debris as it hit, but such impacts had become common in the aftermath of the devastation of the Ring of Iron during the Schism and was not seen as suspicious by the Traitor Mechanicum. However unknown to the traitors, Imperial forces had safely secured themselves within and had successfully infiltrated the Red Planet unnoticed. Once secure on Mars' surface, the combined Raven Guard and Custodes host began a day-long march northwards. As they moved, they fought off attacks by feral technological horrors and cy-carnivora that plagued Mars. The ensuing fight was won, but with the loss of 24 Space Marines and 2 Custodians. After collecting gene-seed from the dead, the loyalists continued upon their path. Along the way they managed to rendezvous with remaining loyal Mechanicum resistance cells on the surface under Skitarii Ordinal Theta Gao before continuing to the Perditum Incendor.^[4c]

Much of the subsequent journey took place beneath Mars' labyrinthine ruins and dune-cities, with the accompanying Skitarii navigating the course. After a weeks march in the darkness, the loyalists finally reached the gargantuan cleft within which the Perditum Incendor nestled. Emerging back upon Mars' surface, they began their assault on the prison-fortress. Raven Guard Commander Agapito Nev and the "Talons" Tactical Squads alongside 24 Custodians struck from the west at one of the three primary bridges into the complex. Corax and his Assault Squads launched a jump-pack assault on the western path. The loyalist Skitarii moved through the centre, and was the first to come under fire from defending Rotor Cannon turrets along the walls. Hiding behind the armoured forms of accompanying automata, the Skitarii then used Castellax robots to tear down the armoured blast doors ahead of them. Meanwhile, Agapito Nev was able to disable enemy turrets by destroying their targeting and power systems and move on to engage enemy Tech-Thralls.^[4c]

For his own assault, Corax descended hundreds of meters into the control bastion of the complex dubbed the Hypocastum. Moving through a contrail of smoke emitted from the Hypocastum's power generators, they were able to land undetected. They then used breaching charges to move into the interior, easily overcoming what meagre prison defences were set before them and encountering far less resistance than anticipated. In their wake came the two other loyalist assault groups, which by now had reached the Hypocastum. Within the lower levels of the complex, Corax found abandoned laboratories and empty jail cells filled with decomposing dead. When they reached the central chamber they found the remaining prisoners piled in a nightmarish display complete with alchemical and occult runes etched in the blood of the executed. Among the dead was the body of Genetor Kephram Unguor. Realizing they had fallen into an ambush, the loyalist Vox network was overloaded with a technological assault as twisted Automata and Daemon Engines rose up from their hiding places around the Perditum Incendor. Corax and his own assault group were beset by massive Brass Scorpions.^[4c]

Among the enemy host now assailing the loyalists were Blood Slaughterers and Decimators alongside corrupted Automata. They fell like a tidal wave upon the loyalists, who quickly withdrew in good order to the entrance of the Perditum Incendor's transit bridge in order to create a chokepoint. The loyalist Skitarii attempted a breakout, but were forced back when their own Automata were infected by Scrap Code and turned upon their allies. It was then that a trio of Ordinatus Aktaeus siege engines arrived under Lukas Chrom, delivering the bulk of the Traitor host. The Custodians accompanying Nev's forces sacrificed themselves to buy enough time for the Raven Guard to retreat back over the bridge and detonate melta charges, preventing the traitors from pursuing them. Meanwhile, the loyalist Skitarii under Gao similarly destroyed their own transit bridge, while the third was destroyed by an unknown faction that the loyalists were not aware of but later revealed to be forces loyal to Kaedes Nex.^[4d]

Corax and Shield Captain Arcas debated what action to take, with the latter demanding they bring down the Penitentiary Tower to bury both sides while the former refused to subject his sons to a meaningless death. It was then that Lukas Chrom entered the battle alongside hundreds of technological horrors. The presence of Chrom immediately broke the debate between Corax and Arcas, and the Raven Guard Primarch threw himself at the traitor overlord. But faced with such overwhelming numbers of formidable robots, daemon engines, and cyborgs, even Corax and the Custodes could not reach Chrom. A gruelling stalemate broke out, but soon enough the superior quality of the loyalist troops took their toll upon the traitors. Chrom had overextended his best troops, and was set upon by Shield Captain Arcas. Chrom activated a Warp Portal to flee, but was badly wounded by Arcas before escaping. Much of the traitor automata lost cohesion after this, but the Daemon Engines were not slowed.^[4d]

With Chrom having fled, the loyalists were able to cut apart much of the remaining enemy forces and regrouped at a cost of over 100 Raven Guard and dozens of Custodes. However the traitors were not defeated, and a fresh wave of Daemon Engines were still incoming over the Hypocastum's cliff face. It was then that Kaedes Nex arrived, having revealed he had covertly traveled to Mars on his own accord and was here to aid his Primarch. He offered Corax escape through the same hidden tunnels he had used to enter the Hypocastum. The surviving Raven Guard and Custodes fled through this corridor as Gao's loyal Skitarii detonated the Perditum Incendor's plasma reactors, bringing the entire prison-compound down upon itself. After several days beneath Mars, the loyalists were led by Nex to his own hidden evacuation craft. The loyalists used these to escape back into orbit and dock with the Sojourn.^[4d]

In the aftermath of the battle, a vengeful Chrom led a brutal purge of surviving loyalist Mechanicum cells on Mars somehow taken from Gao's deceased Skitarii. While he had failed to eliminate Corax or the Custodes, Chrom nonetheless was hailed for scoring a great victory amongst the larger Dark Mechanicum. For the loyalists, the ambush made the forces of the Emperor more suspicious of their own intelligence networks.^[4d]

The Arca Silentus

Arca Silentus Raid Conflict Horus Heresy Date 013.M31 Location Mars/Oort Cloud Outcome Loyalist victory, nearly all loyalists slain or missing Combatants Imperium New Mechanicum Commanders Centurion Aster Crohne (MIA) Shield Captain Sola Morvae Arcas (MIA) Lukas Chrom Strength Blood Angels 94th Company 200 Custodes Loyalist Skitarii cells Custodes Cruiser Sojourn 2 Dark Angels Destroyers Capita Aquilae Battle-Automata Many thousands of Tech-Thralls, Mutants, Cyborgs, Daemon Engines, and Automata Arca Silentus Casualties All dead or missing, 36 Dark Angels and 19 Custodes later recovered Unknown

By 013.M31, the Battle of Beta-Garmon had been won by the Traitors and Horus was preparing to assault Terra directly. Dorn feared that blockaded Mars would be a tumour within his defensive network in the Sol System that the traitors could exploit. His fears were seemingly confirmed, when a beacon on Mars activated to connect Scrap Code to distant control stations within the Oort Cloud. Fearing that the loyalist defensive network would be disrupted by this device, Dorn ordered its destruction paramount before the arrival of Horus' fleet. With the Emperor Himself having forbidden Exterminatus due to Mars' technological and industrial value, Dorn's only option was a surgical raid to destroy the Traitor beacon.^[4e]

Sanguinius, by now on Terra with his Legion, was the one who proposed a solution. Offering up the Blood Angels 94th Company under Aster Crohne for the operation, the unit had long stood outside their Primarch's favour due to it being composed entirely of Terrans and Inductii save for a single Baalite warrior. The Custodian Guard also offered up the cruiser Sojourn once more under the command of Shield Captain Morvae Arcas. The highly advanced vessel moved all the way to the edge of the Sol System in a span of hours via precise Warp jump. They arrived as close to the point of the scrap-code transmission as they could, coming under fire from corrupted attack satellites that made up the Oort Cloud's defences. The Custodes targeted the satellite cluster's command and production station, the Arca Silentus.^[4e]

The Custodes knew disabling or destroying the Arca Silentus was paramount to their mission, and with the Sojourn's guns useless against such a massive edifice opted for a boarding operation. 200 Custodes were transported via teleportation deep into the station, where they discovered it a heavily corrupted fusion of flesh and machine. The Custodes fought through waves of corrupted automata to reach their target, with only a single Custodian falling while hundreds of the heretical machines were destroyed. However as soon as these foes were destroyed did the Ars Silentus automated production systems unload another wave of robotic warriors, this time even larger and crueler than the prior one with flame and melta weapons that could melt the armour of the Custodes.^[4e] By now the Ars Silentus had blasted the Sojourn into two. Not even Chaos Decimators could best the Custodes when they worked together in groups, and the battle was waged for hours. As they moved deep into the interior of the corrupted station, many of the Custodes became separated and could not reestablish contact with one another due to the scrap-code interference.^[4f]

As the Custodes battled on the Arca Silentus, the Blood Angels 94th Company alongside allied loyalist Automata under Magos Domina Erane Shurol was launched from the Lion's Gate Spaceport towards Mars. After moving past the loyalist blockade, their dropships soon fell victim to Traitor Scrap-Code and were forced to make an emergency landing in the Martian desert some distance from the beacon revealed to be under the control of Lukas Chrom. The loyalist raiding part was immediately set upon by waves of twisted machines, Daemon Engines, and corrupted cyborgs, and a brutal melee broke out.^[4e]

The loyalists were quickly pinned in place due to the sheer number of foes set against them, but the bulk of Archmagos Shurol's automata allowed them to endure the enemy waves. The loyalists were beset by scrap-code through the battle, effecting their Machine Spirits even in devices such as Bolters. Crohne realized they could not hold this position indefinitely, and ordered a breakout attempt. The automata threw themselves forward at the foe as the Space Marines sought to push on to their target, sacrificing 50 of his own warriors to hold back the foes coming at their back.^[4f]

Having sacrificed so many of his warriors, the Blood Angels had scant progress as more enemies appeared to harry them. However just as they were about to be overrun by a fresh wave of mechanical foes, loyalist Martian Skitarii guerrillas appeared to aid the 94th Company. This bought the Blood Angels precious time to continue towards their objective, but all hope seemed lost when a traitor Titan heavily corrupted by the Ruinous Powers appeared over the horizon. The loyalist Skitarii again came to the rescue of the Blood Angels, using a hidden Ordinatus engine placed nearby to fire upon the God-Machine. After two shots, the Titan's head was destroyed and it fell to the ground. The majority of Chrom's host fled after witnessing the destruction of the Titan. After the battle, the Blood Angels continued towards their objective while the Skitarii resistance fighters pursued the fleeing enemy.^[4f]

For their part, Archmagos Shurol's badly damaged Cybernetica host took up positions around the fallen Titan to make a final stand against the enemy to cover the Blood Angels as they finished their mission. After a nights march, the Blood Angels finally came upon Lukas Chrom's stronghold and the source of the Scrap-Code beacon. However the entire complex was defended by a sea of Daemon Engines and Robots of all sizes and types, and with only a scant hundred warriors the Blood Angels mission seemed hopeless. This did not deter Crohne, and he ordered a charge into the enemy ranks.^[4f]

Meanwhile back in space, the Custodes continued to battle deep within the Arca Silentia. They eventually came to the forge at the heart of the station that birthed the enemy automata in endless streams. Arcas' detachment of Hetaeron Guard immediately turned to hold back the foe as Arcas and his men planted melta bombs on the heart. But even after the forge-heart blew apart, the Arca Silentus did not die. Warp energy coalesced and a new heart was born in its place, immediately vomiting forth a stream of pure Daemons. It was just then that the Custodes were saved by two Destroyers from the Dark Angels, which had been independently tracking the scrap-code beacon of the Arca Silentus themselves. As the Custodes made one last final charge against the enemy, the Dark Angels vessels engaged the kill-satellites around the station. Realizing their meagre weapons were not enough to destroy the ever-mutating Arca Silentus, one of the destroyers was torn apart from an organic arm which spawned from the station.^[4f]

The death of the destroyer would not be in vain however, as the surviving Dark Angel vessel was able to plunge deep into the station through the damage it had caused to unleash a salvo of Torpedoes at the heart, where the Custodes beacon was strongest. After initiating an emergency teleportation, the badly damaged Dark Angels destroyer pulled away as the warp rift at the heart of the Arca Silentus ruptured, destroying it. The grievously wounded Dark Angels ship then drifted throughout the Oort Cloud, none aware of its sacrifice. Later in 022.M31 after the Heresy had been won, the vessel was recovered by Imperials who discovered 36 Dark Angels and 19 Custodes in stasis aboard.^[4g]

Back on Mars, Crohne continued his desperate struggle as his Inductii charged into the enemy to buy time for the veterans of the 94th to complete their objective. The only Baalite member of the 94th, Leviathan Dreadnought Hammonah, fought most viciously of all as Crohne pressed towards the beacon. A Brass Scorpion now appeared and charged into the Blood Angels' ranks, snatching up Crohne with one of its claws. But before Aster Crohne could meet his end and be fully crushed, Hammonah seized the claw and tore it from its socket. Another Leviathan Dreadnought appeared, unloading Cyclonic Melta Lances into the face of the Daemon Engine which finally died. A badly wounded Crohne continued on, but was beset by two more gigantic Brass Scorpions. However the Blood Angels were saved from certain doom by the destruction of the Arca Silentus, which caused a huge feedback surge in Scrap-Code across the traitor constructs. Every Blood Angel able to move now broke into a run towards the beacon.^[4g]

Crohne, now only with one hand, confronted Lukas Chrom himself. He found his command throne empty save for a cohort of Thallax. As he battled these foes, Crohne noticed that the scrap code surge was abating and the enemy walkers were now regaining cohesion. The battle would have ended there save for Hammonah, who tore a plasma reactor from one of the mechanical creatures before him. He then threw it at the scrap code beacon's own generator, causing a catastrophic meltdown that took the entire structure with it. Hammonah died in the process, but his sacrifice had finally allowed the Blood Angels to achieve their objective. The remaining Blood Angels prepared to fight to the end against what foes remained, trapped on traitor-occupied Mars.^[4g]

Aftermath

The traitor victory at Mars was both a significant and symbolic blow for the Imperium, and it forced acting loyalist commander Rogal Dorn to enact a naval blockade of the world for the rest of the war overseen by the Imperial Fists and Imperialis Armada.^[5] As Dorn was focusing on building up the defences of Terra, he did not have the resources to reclaim Mars for the time being, though several raids were conducted as part of the Shadow Wars.^[4a] There were several violent breakout attempts by the Martian traitors, though the Imperial blockade would be lifted until the Solar War.^[5] With the traitorous Fabricator-General Kelbor-Hal and his inner circle trapped on the Red Planet, Hal's Disciples rose in influence in Horus' court.^[6]

Ultimately, Mars would not be reclaimed for the Imperium until after the Battle of Terra.^[2]

Sources

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• 1: Mechanicum (Novel):
  • 1a: Chapter 1.03, pg. 64
  • 1b: Chapter 1.05, pg. 113
  • 1c: Chapter 2.01, pg. 186
  • 1d: Chapter 3.03, pg. 355
  • 1e: ^[Help]
• 2: The Horus Heresy Book Six pg. 30
• 3: Secrets of the Solar War — Day 1
• 4: Campaigns of the Age of Darkness: The Martian Civil War:
  • 4a: pgs. 15-21
  • 4b: pgs. 22-27
  • 4c: pgs. 31-33
  • 4d: pgs. 35-43
  • 4e: pgs. 47-53
  • 4f: pgs. 55-63
  • 4g: pgs. 64-65
• 5: The Solar War (Novel), Chapter 22
• 6: The Lost and the Damned (Novel), Chapter 17
• 7: Legions Imperialis: The Rise of the Dark Mechanicum, pg. 50
• 8: Journal Tactica: Skitarii
  • 8a: pgs. 8-9
  • 8b: pgs. 14-17
  • 8c: pgs. 18-21