Battle of Calth

The Battle of Calth, also referred to as the Calth Atrocity, was the name given by later Imperial scholars to the treacherous campaign conducted during the early stages of the Horus Heresy by the traitorous XVII Legion Word Bearers on the behalf of Warmaster Horus, in the attempted extermination of the XIII Legion Ultramarines, as they presented a serious threat to the Warmaster’s heretical rebellion against the Emperor of Mankind.

Striking a Blow for Horus
During the opening days of the galaxy spanning conflict that would see the galaxy burn, Warmaster Horus launched his treacherous attack against the few Loyalist elements within each of the Legions, which approximated one-third of all the Space Marine Legions under his command, upon the world of Istvaan III. Having successfully purged these elements, Horus plotted the next stages of his insurrection against the ‘False Emperor’. With word received of the Warmaster’s treachery by a small contingent of Loyalist Space Marines under the command of Captain Nathaniel Garro, formerly of the Death Guard Legion, the Emperor ordered the deployment of seven Loyalist Legions to bring Horus to account for his actions.

It was while Horus made his plans for what would become known as the infamous Dropsite Massacre on Istvaan V, that the Warmaster sent word to the XVII Legion’s Primarch Lorgar of the Word Bearers that now was the time to strike. The Warmaster was keenly aware of the bitter hatred that Lorgar had for his Primarch brother Roboute Guilliman and his XIII Legion Ultramarines. He told Lorgar of the false intelligence that he had fed to Guilliman in regards to a possible theoretical within the Veridian System in the Segmentum Tempestus, far to the galactic south. This supposed ‘threat’ stemmed from the Orks of the Ghaslakh empire. He had ordered the XIII and the XVII for mustering and conjunction at the world of Calth, in order to conduct a massive joint-campaign of compliance against the Ghaslakh xenohold.

It would be at Calth that Lorgar would launch a surprise attack on the Ultramarines whilst they were gathered. The Loyalist XIII Legion would be caught completely unawares and the XVII Legion would be able to annihilate the upstart Ultramarines. The Calth Conjunction would be an opportunity to be seized by the XVII to demonstrate their new alignment to the Ruinous Powers and to Warmaster Horus. The choice of Calth was not chosen by chance. This was to be an opportunity to hurt and shame the Legion that had chastised them all those years ago. By being the instrument of the savage reprimand on the world of Khul forty-four years earlier, the Ultramarines had made themselves a target. They had made all of Ultramar’s Five Hundred Worlds targets for the Word Bearers’ righteous vengeance.

The majority of the XVII Legion was ordered to the Ultramar System, the powers of the warp giving them sure and swift passage across the restless Immaterium. As the Word Bearers entered Ultramar space, Lorgar prepared his Legion for the inevitable slaughter that would soon follow. Command of the main assault force was given to Kor Phaeron, First Captain and one of Lorgar’s most favoured champions. Kor Phaeron bore a deep and abiding hatred for the Ultramarines. Calth was to be Kor Phaeron’s operation, far more than it was Lorgar’s. Kor Phaeron had planned this for his Primarch meticulously, and executed it with the aid of the Dark Apostle Erebus. The punishment and annihilation of the XIII was its principal aim; the humiliation and execution of the wretched Roboute Guilliman. But it was also an advancement; another step on the spiral path of the Great Ritual. It would allow their beloved Primarch to progress.

The first phase of their plan involved in the capturing a vessel of the XIII Legion. The Word Bearers waylaid the Ultramarines vessel Campanile which was patrolling the outer rim of the system, boarding it and taking it over. They would then use the captured vessel to stage a terrible accident so that they could capitalise on the Ultramarines’ mercy. While they stayed their hand the XVII would take full advantage of the situation and commit murder most foul against their hated rivals.

The Calth Conjunction
Calth was once a verdant Agri-World whose manufacturing output at the time of the Horus Heresy, would have soon rivaled Macragge within only two to three more decades. There was even talk of a projected superorbital plate like those employed by Terra. The master worlds of the Imperium all had such plates. Calth would join Macragge, Saramanth, Konor, Occluda and Iax as one of the master worlds of the Ultramar sector, and between them, would govern a vast swathe of the Segmentum Ultima. Calth would become one of the anchor points of the coming civilization at the successful conclusion of the Great Crusade.

Roboute Guilliman and a sizeable portion of the XIII Legion had been stationed near the moons of Saturn when they received their false orders from Warmaster Horus. Some within the Primarch’s command questioned the need for a compliance force the scale of which hadn’t been seen since the Ullanor Crusade or the early days of the Great Crusade. They had seen the tactical audits and knew that the Ghaslakh greenskins were a joke, their overall threat being over-sold. But wiser, more experienced Chapter Masters realised the need for such a compliance, for it was designed to achieve two objective, and neither of them was military. The Ultramarines were to lend a little shine to the ungainly reputation of the Word Bearers by operating in concert, and the XIII was to demonstrate the glorification and authority of the Warmaster.

Regardless of their trepidations or personal feelings, Guilliman acquiesced to Horus’s commands and moved his Legion to the world of Calth in order to rendezvous with more elements of the Ultramarines and take on supplies. They would then join their fellow Legion in this conjunction and share in the martial effort of crushing the greenskins. But truthfully, Guilliman still had misgivings of the actions taken against the XVII Legion during their chastisement at Khul. To have the XIII Legion used as an instrument of humiliation and as an example of perfection, did not sit comfortably. Guilliman was concerned that things would never be right in their relations with the Word Bearers. Guilliman felt that Horus Lupercal was demonstrating his wisdom and perception right at the beginning of his command as Warmaster. He was attempting to heal old wounds, actively working to set two of his largest Legions at ease with each other and close the bitter rift.

Signs and Portents
There were many clues of the coming tragedy that would soon take place. There were many portents. Given the extraordinary thoroughness with which the XIII Legion maintained its readiness, it might have been considered tragic, or incompetent, that so few were heeded. The simple truth of the matter is that, in this instance, the Ultramarines did not know what to look for. The first signs occured when there was some minor interruption in the vox traffic which was soon attributed to solar distortion – for the void was known to forever creak and whisper around the audible and electromagnetic ranges. Soon there were various reports of those that heard voice singing on the vox-link. This chanting soon blocked out the main orbital data-feed with the surface of Calth for period of only seconds. Its source is unidentified. An hour later, there were two more bursts, which were also unsourced. Communications Control reported an hour later that there were ‘a series of malfunction events’ and warned that further communication disruptions might be expected during the day until the problem was identified. An hour after that, on the night side of Calth, the first of the bad dreams began.

There were psychic portents as well. There were hundreds of Ultramarines Battle-Brothers that had been Librarians before the Emperor's decree at the Council of Nikaea banned the Space Marine Legion’s use of psykers. Many resented the Decree, but honoured their oath to the Emperor and surrendered their Librarian panoply and wargear, returning to the lines as ordinary Battle-Brothers. Before the attack on Calth, those gifted with psychic abilities suffered severe headaches and pain behind the eyes. They ignored the pain, chalking it up to nothing more than fatigue after having gone without rest periods for several days during the preparation phase for the coming campaign against the Orks. It had not been possible to shut down higher mental functions and sleep, or at least remedially meditate. This mysterious pain was actually a warning sign, of the impending approach of the Forces of Chaos. They all ignore the headaches. Few survived the events long enough to regret it.

Below, on the planet’s surface there were hundreds of landing camps of the XVII Legion and its army auxiliaries, landing camps which were spread across the surface of Calth. For days, these principal cult echelons chanted monotonously as they conducted sacrificial rituals. Eight names were now imbedded into the system. Eight names broadcasted into the dataflow of the Imperial communications network. No filter or noospheric barrier would block them or erase them, because they were only composed of regular characters. They were neither toxic code nor viral data, but once they were inside the system, and especially once they had been read and absorbed by the Mechanicum’s noosphere, they began to grow. Soon these names became combinations of letters and then meanings. These implanted meanings were caustic, infectious and indelible. There were eight of them, the sacred number of Chaos – the Octed.

At the orbital Watchtower, located at the Kalkas Fortalice, Mechanicum Server Uhl Kehal Hesst, Server of Instrumentation, detected scrapcode within the system – the dull amber threads of diseased information buried in the mass of healthy data. There was 2% more of it than any Analyticae projection had calculated for the Calth noosphere, even under the irregular circumstances of the conjunction being conducted. This was an unacceptable margin. The Mechanicum reported their findings to Guilliman. They inform the Primarch that the scrapcode problem had been identified as a hindrance and that, though regrettable, these things did often happen.

First Strike
Multiple Word Bearer vessels had already arrived in-system, which included at least a half dozen or so crimson coloured vessels. Counted amongst their number was the massive Infidus Imperator – the Grand Cruiser and flagship of Kor Phaeron, as well as Destiny’s Hand, the Battle-Barge of Dark Apostle Erebus. The Dark Apostle was tasked with a vital mission on behalf of the Warmaster. While the rest of the XVII Legion’s vessels stationed themselves rearward of the massive orbital flotilla, he teleported down to Calth’s surface, to the Satric Plateau, located 2,000 kilometres north of Numinous City. Covered in frost from the hard winter, this particular area was selected as the best potential site to conduct the blasphemous ritual in which he was to perform, for the Immaterium vectors aligned perfectly and the skin of the empyrean was particularly thin. The Ruinous Powers had manufactured this perfection at exactly the right time.

A Word Bearers strike team awaited the Dark Apostle, its leader was Essember Zote, one of the dreaded Gal Vorbak. He had a work party of the Tzenvar Kaul, “The Recursive Family”, one of the primary cult echelons. This was to be the point of the true conjunction. The men of the Kaul laid out a circle of polished black rocks upon the ground, each taken from the volcanic slopes of Istvaan V and marked with a blasphemous sigil. These were arranged in a perfect circle a kilometre in diameter. These rocks were summoning stones, whose latent power within them could make one sick just holding them.

The men of the Tzenvar Kaul approach the summoning circle, each carrying other offerings from the Istvaan system. Marching in procession, they bore along portable stasis flasks, the fluid within them are murky with blood. They contain harvested Progenitor Glands and Gene-Seed. The lost life of betrayed souls now offered for the final blasphemy. There were Salamanders gene-seed, Iron Hands and Raven Guard. Knowing the Ruinous Powers made no distinctions there was other gene-seed there besides: Emperor’s Children, Death Guard, Night Lords, Iron Warriors, Word Bearers, Alpha Legion, even Luna Wolf. Any that fell during the secret abominations of Isstvan III or V were deemed suitable.

The Kaul start to carry the flasks into the circle. The moment they crossed the stones, the bearers started to whimper and retch. Several passed out, or suffered strokes, and fell, smashing the flasks. As the moon rose into perfect alignment, Erebus took his vox-link and sent a messenger to his co-conspirators in orbit. Aboard the docked Ultramarines vessel, the Samothrace, Captain Sorot Tchure of the XVII was enjoying a formal dinner arranged by his Ultramarines counterpart and ‘friend’, Honorius Luciel, Captain of the 209th Company. Receiving his order to carry out his part of the plan, Tchure returned back to the dining table with his fellow Word Bearers. As the two Captains struck up a conversation, the Ultramarines Captain was aware that his counterpart seemed agitated.

Tchure shared with Luciel that he had recently learned a bit of useful warcraft whilst fighting in the Istvaan System that he thought the Ultramarines Captain would appreciate. Unaware of any recent campaigns within the Istvaan region, Luciel's interest was piqued. The Word Bearers Captain spoke of the art of betrayal and its inherent power because the treachery ran so deep, especially if it was committed against a trusted ally or close friend. Asked to join the advance into the Ultramar system, he told Luciel that he had to prove his commitment. The Word Bearer subtly tried to warn his friend that in order to show that he was loyal to the XVII Legion’s new cause he must first betray his friend. Realising, too late, the meaning of Sorot’s obscure warning, Captain Luciel rose to his feet to defend himself, but was cut down with a well placed plasma shot through his chest. Tchure and the rest of his Word Bearers then opened fire upon the startled Ultramarines, killing their entire entourage. They were than offered as a sacrifice to the Ruinous Powers - the first casualties of the Battle of Calth.

Aboard the bridge of the Samothrace, an alarm sounded to the officer of the watch, the ship’s system notified him of a malfunction. Access his computer for clarification he was shocked when he saw the phrase [Weapons discharge, company deck]. Activating the vox system and rousing deck protection, the officer of the watch began to cordon and secure the entire company deck. Suddenly, general quarters was sounded, as the bridge came alive with a cacophony of various alarms, klaxons and bells all screeching and booming; the proximity alarm, the collision warning alert, the course defect advisor as well as many others. Looking at the main screen for visual verification, what happened next, happened too fast for anyone to see.

Opening Gambit
The captured Ultramarines vessel Campanile had crossed the inner ring, its codes accepted by the orbital defence grid. The mass of the fleet disposition lay ahead of it as well as the orbital dock yards. As it passed within the orbit of Calth’s moon, it began an abrupt acceleration. The captured vessel screamed into Calth’s orbit like a streaking projectile fired from a bolter, directly for the Calth Yards, the fledgling beginnings of the planet’s first proper superorbital plate. It somehow managed to miss some of the larger vessels, grazing them with its shields and skimming the surface of others. Smaller craft that lay in its path were utterly annihilated; cargo boats, lighters, ferries, maintenance riggers. The Ultramar Azimuth Graving Dock is vaporized by the massive bulk of the runaway vessel. Several vessels suffer catastrophic hull damage and multiple manufactory modules are destroyed, instantly killing thousands of artificers and engineers. The Campanile continues its suicidal orbital run.

Still moving, the captured vessel punched through a hollow spheroid that housed three separate vessels, obliterating them all. The assembly ruptured and the debris was propelled into attached habitat modules, voiding them into space. Multiple smaller craft are destroyed in the process. The devastating trajectory of the Campanile causes the Calth Veridian Anchor to shudder under the onslaught. Internal explosions occur throughout the structure as even more ships are destroyed or catastrophically damaged. Larger battleships explode as their critical damage is compromised by its power plants and vast ammunition stockpiles. Huge, burning sections of the yards superstructure as well as the debris of destroyed vessels rained down upon the surface of Calth. The Ultramar Zenith Graving Dock suffered integral gravimetric failure and dropping out of orbit, twisting and breaking as it plummeted to the planet below. The massive grand cruiser, Antrodamicus, supported by the dock, ripped free of its moorings and slid backwards, caught in the gravity of Calth. With its drives off-line it had no power to stabilise itself or prevent its inevitable doom.

The Campanile continued to move, shooting forward like a solid projectile, a gargantuan mass of metal. It annihilated a pair of slipways and the ships within them, ramming through the vital data-engine hub and destroying multiple data-engines as well. As the automatics failed and the noosphere experienced a critical and fatal interrupt, the yard’s core was obliterated, killing over 35,000 individuals. The Campanile finally breaks up, still traveling at immensely high realspace velocities, a large portion of the doomed vessel spun out of control and destroyed a battleship. The remaining pieces of the Campanile clear the far side of the Calth Veridian Anchor and rained down, burning like meteorites, upon the surface of the planet.

Aboard the Samothrace, Sorot Tchure performed his second ministry. His men kill most of the ship’s primary crew. Advancing to the main bridge, burning through blast hatches that had been closed in desperation, Tchure confronts the ship’s Captain, who solemnly announces his disinclination to assist the traitorous Word Bearer. Ignoring the officer, Tchure brutally kills the senior officer, letting the body drop to the deck. The bridge crew quickly realise that their serves are not required. The Word Bearers proceed to murder the entire bridge crew. The Battle of Calth has begun in earnest, as the Word Bearers and their cult echelons begin forming up in their thousands for their brutal assault upon the surface.

Battle of Calth
The vast shipyard of Calth Veridian Ancho is damaged beyond the possibility of salvation or stabilization. With the destruction of the main data-engine hub the Mechanicum’s ability to communicate has been torn out and its systems compromised. The Calth high anchor rages in a firestorm. The grievous injury to the Ultramarines fleet and the orbital yard infrastructure as well as the death toll is unthinkable. Within the few seconds after the initial impact, ships across the high anchorage attempted to desperately power up their drives and bring their weapon systems back online. Some attempted to generate enough power in the vain hope of raising their shields or prepared their ships to slip authroised moorings in order to reposition in case of an attack.

Then a massive ship opens fires. This massive grand cruiser is known to the Ultramarines as the Raptorous Rex, but it has been renamed, with as little notice as the Word Bearers gave when they changed the colour of their panoply, the Infidus Imperator (“False Emperor”). This mighty vessel is the flagship of Kor Phaeron. He orders his ship to discharge all of its primary lance weapons at the battle-barge Sons of Ultramar, obliterating it in one brutal salvo. The Infidus Imperator chooses its next target. In formation behind the mighty craft, the Crown of Colchis starts to fire too. So does the battleship Kamiel. So does the Flame of Purity and the Spear of Sedros as well as the flagship of Dark Apostle Erebus, the battle-barge Destiny’s Hand.

Shipmaster Ouon Hommed, Captain of the heavy destroyer Sanctity of Saramanth, sees the Infidus begin its merciless prowl along the anchorage line. He understood precisely what the vast Word Bearers vessel was doing. It was executing the ships in the line beside it the way a man might execute a row of helpless prisoners. The Sanctity was sitting at slip cold, drives tamped down. With the best will in all the worlds, it will take 50 minutes to rouse the ship to operational readiness. This was true of the entire fleet. The starships of Ultramar were sitting cold at high anchor for the conjunction. All of their power plants were at lowest yield for the purposes of maintenance, loading and embarkation checks. None of them needed ready drives or weapons or shields. They were all under the protective aegis of the planet’s weapon grid. Every ship was powered down at the time of the attack, which is why they were all helpless and shield-less now.

The Infidus Imperator was coming, moving down the line of vulnerable Ultramarines vessels trapped in their moorings. So were other ships from the Word Bearers fleet. It wasn't that they were perceived as responding hastily. It wasn't that they were taking wild shots at imagined targets before finding out what was really going on. It was the mere fact that they were moving at all. The ships of the XVII Legion weren’t powered down upon their arrival. They were sitting at anchor hot, for they knew what was coming and lay in wait. The Word Bearers continued their onslaught of the Loyalist fleet unabated, leaving Primarch Guilliman to witness their perfidy first-hand.

From Bad to Worse
Shortly after the Campanile explodes in orbit, the datashock from the resulting scrapcode kills Adeptus Mechanicus Server Uhl Kehal Hesst with major datashock (also known as hypertraumatic inload syndrome). Light hit the orbital Watchtower at Kalkas Fortalice a nanosecond after the shock wave of data. The noosphere immediately collapsed. The tower’s manifold field stuttered out. Hesst felt and absorbed the shared agony of several thousand deaths: his modified brethren aboard the primary shipyard, aboard docked vessels, in the tower around him. With the death of Hesst and the surrendering of the bioengines, all the orbital automatics died. Calth’s planetary weapons grid ceased to function, leaving the entire XIII fleet vulnerable to attack.

Fortunately Hesst’s second-in-command, Meer Edv Tawren, Magos of Analyticae was not killed by the infected scrapcode. It was simple Mechanicum protocol that saved her life. When dealing with a significant scrapcode problem, the server has his second-in-command unplug so that there is no danger of the second-in-command being compromised by the scrapcode. It was an operational safety measure. It saved Tawren from far more than just a scrapcode infection. When Hesst died in her arms, he charged his second to connect herself to a working server to attempt the reconstruction the noosphere and restart the defence grid, in order to bring the orbital defences back online. Magos Tawren would play a pivotal role in the coming conflict.

Debris began to fall from the clouds, trailing fire like meteorites, raining across the fertile river valley. They struck rivers and across the rooftops of Kalkas Fortalice. Some of the heavier pieces of falling debris struck buildings, exploding them like artillery strikes. The hail of debris had only begun as larger objects begin to fall – parts of ships, orbitals and the docking yards. Magos Tawren saw the unfolding disaster before her sensori did. She saw the grand cruiser Antrodamicus falling backwards into the atmosphere, stern first, towards Kalkas Fortalice.

Meanwhile, unbeknownst to the Ultramarines, Kor Phaeron materialised aboard the Samothrace through arcane means. The Word Beaers used the Samothrace to slip past the Ultramarines into the gates of the Zetsun Verid Yard. Behind it, Calth’s main shipyard continued to burn. No one challenged the Samothrace for it was a vessel of the XIII fleet running for cover, and besides, the vox was choked and the noosphere was dead. No one aboard the Zetsun Verid Yard questioned the fact that the yard structure had remained untouched either. A fact the Ultramarines had overlooked, for it was a vital specialist facility, and the yards around it had been targeted and obliterated. The Samothrace pulled into the ship docks between two fast escorts sheltered in the yard space. The Ultramarines put up intense resistance, but eventually the Zetsun Verid Yard also fell to the Word Bearers. Their only setback was that the destruction of the noospherics was so complete, that it took their Dark Mechanicus allies longer than expected to recreate a workable network. Zetusun Verid contained a vital advanced engine hub capable of substituting itself, in the event of an emergency, for the primary orbital hub of Calth Veridian Anchor.

The shadow Mechanicum brought the Zetsun Verid Yard systems online, its data-engine resumed operation. Sensing that the planetary weapons grid was inactive, and that the inactivity had been caused by the inexplicable loss of the data-engine hub located aboard Calth Veridian Anchor, the engine automatically obeyed protocol and assumed control, taking up the reins of the grid system. The Calth weapons grid went back on-line as its manifold re-ignited. The Word Bearers were now in control of the effective firepower of a major fleet. The firepower of this defence system was distributed across the surface of Calth and its orbit. Kor Phaeron had the Dark Mechanicus magos bring on-line the 962 orbital platforms as well as several ground-based stations, including the polar weapon pits. It took approximately 10 minutes before authority lights flickered green along the master control room’s main console. Calth had a weapons grid capable of keeping at bay an entire expedition fleet or primary battlegroup. Only the most devious and ingenious treachery had circumvented it on this dreadful day. The weapons grid soon began to discharge. Calth began to kill the neighbouring planets in the Veridian system.

The Ultramar fleet was scattered, having been reduced to about a fifth of its original strength. Those vessels that remained were either fleeing to the far side of the local star to avoid fleet attack or the inexorable fire of the weapons grid or, like Primarch Guilliman’s flagship, the Macragge’s Honour, they lay helpless and drifting in the high anchor zone. There were virtually nothing left to fight with. It was simply a matter of the Word Bearers picking off the last few fighting ships of the XIII fleet. The weapons grid had no difficulty doing that. It destroyed the local forge world of Verida Forge, a small moon with offensive capabilities, a starfort near the system’s Mandeville Point, and several capital ships.

First Chapter Commander Marius Gage was the first to see a clearer picture of the attack pattern of the Word Bearers’ fleet. Of the surviving Ultramarines vessels, many of these surviving ships were the largest and most powerful capital ships. With the traitors firmly in control of the weapons grid they could easily pick off the most serious threats at their leisure. Those ships that had been spared were all helpless and drifting, like the Macragge’s Honour. The moment they shook off the effects of the scrapcode or the electromagnetic pulse, moved or raised shields the grid destroyed them. The Word Bearers intended to take as many of the XIII Legion’s capital ships intact as they could. They wanted to bolster their fleet with warships to build their overall striking power. They wanted to turn the Ultramarines’ ships against the Imperium.

Calth Besieged
The savagery and perfidy of the Word Bearers’ assault left the Ultramarines reeling in shock. Their fleet had been decimated and was scattered. Entire planets had been destroyed. Hundreds of thousand Chaos cultists stationed on Calth attacked their former Loyalist allies of the Imperial Army, attempting to destroy them in the name of the Warmaster Horus and the Chaos Gods. The forces of the Word Bearers numbered over 100,000 Space Marines. They also received aid from traitorous elements of the Dark Mechanicus, whom supplied them with a large host of war engines, included amongst their number, the fearsome Titans. Throughout the planet the fighting was brutal and intense. The savagery of the Word Bearers’ assault threatened to overwhelm the beleaguered defenders within a matter of hours. However, Kor Phaeron had underestimated the tenacity and resolve of the Ultramarines.

At Barrtor, two Ultramarines Captains from the 111th and 112th Companies decided to consolidate their Companies, the Imperial Army, the Mechanicum and the Space Marines of the XVII Legion. They would form up, than pull back east into the Sharud Province. The quickly realised that if they did nothing, they would be killed by the falling debris bombardment. Captain Phrastorex of the 112th decided that he would link up with the Word Bearers while Captain Ekritus would lead both Companies to the province. Taking a detachment of his Honour Guard the 112th Commander walked down the slope to the flood plain where the XVII Legion had made base camp. He observed their forces already had their tanks started up and their Legionnaires formed up. Advancing up the hill to meet him he sees a line of red armoured warriors. As Phrastorex raised his hand in salutations the Word Bearers open fire. Unable to comprehend this atrocious act of treachery, the Space Marines of the XVII Legion continued to massacre the Ultramarines Captain and his men. Captain Ekritus witnessed the massacre, and was eager to visit his vengeance upon the traitorous bastards but was restrained by his men. Then, without warning, the Titans began to open fire on their position.

The shattered remnants of the 111th and 112th Companies retreated into the burning woods of the forest located east of the Boros before the reaping assault of the betrayers. Achilles and Proteus pattern Land Raiders, coloured in crimson and adorned with abominable designs, demolished the tree cover and Loyalist Space Marines alike. Captain Ekritus managed to find a position above the treeline and observed the destruction before him. He could see the vast hosts of the Word Bearers and their auxiliaries assaulting the towns along the river and the port. There were waves of soldiers, tens of thousands strong, armour formations of Titan engines as well as phalanxes of red armoured Space Marines. The Ultramarines Captain observed in horror, as the XVII Legion’s assault swept aside everything in its path.

There were bodies everywhere; civilians, Imperial Army, and far too many Ultramarines. Men lay dead with their weapons still sheathed or covered, cut down without the opportunity to face their deaths. Heaps of cobalt-blue armour that contained limp corpses lined the roadways and arterials. Some had been stacked against fences and walls like firewood whilst other had been cut open and emptied. A few had been nailed to posts, or against the sides of buildings. Some appeared to have been butchered or…eaten. This was desecration, not a just war, but a war crime. It defied and shamed the codes and precepts of the Legiones Astartes, codes and precepts set down by the primogenitor Emperor. The Word Bearers had perverted any semblance of the true and legal path of the Imperium, or the moral code of mankind.

Desperate Hope
The doomed Antrodamicus demolished a large swathe of destruction through the once teeming city of Kalkas Fortalice, clearing a patch two and a half kilometres wide. Meteoric debris continued to slice down from the sky all around it, bombarding the city and the surrounding landscape. Fortunately, Magos Tawren managed to flee the destruction of the Watchtower before the large vessel struck the planet’s surface. Little information about what had recently occurred was gathered by the survivors on the planet’s surface. There had been some sort of major orbital incident, either an accident or attack. There was obviously a considerable fleet loss, considerable loss of support infrastructure as well catastrophic collateral damage suffered on the surface due to the orbital destruction. But as the starport was now gone and all vox-links were out, no one possessed the ability to communicate with other possible surviving surface units. And with no data feed available there was no way to estimate the type or extent of the situation.

Eventually, Magos Tawren and her loyal Skitarii forces managed to consolidate their forces with a few surviving Space Marines from the 4th Company, including Captain Remus Ventanus. Assessing their desperate situation, the Captain realised he had a vast horde of cultists arrayed against his forces as well as hundreds of thousands enemy Space Marines. The traitors also possessed dozens of giant war engines within their ranks. Magos Tawren suggested seeking refuge at Leptius Numinus, the old gubernatorial palace on the plains. They possessed a non-active but functional data-engine as well as a high-cast vox array. Though not currently operational they were continuously maintained, and because their systems were off-line, they might have been spared the scrapcode infection and electromagnetic damage. If they could reactivate the data-engine they might be able to contact the fleet.

The commander of Tawren’s Skitarii suggested that they utilise their dedicated emergency manifold, which is used as a crisis back-up, to contact other possible surviving Ultramarines, Imperial Army or Mechanicum forces. The Loyalist Captain eventually established comm-links with other besieged Ultramarines. His situation was not unique. In fact all of the Ultramarines on Calth seemed to be in the same predicament. Of the fate of the Ultramarines Primarch, none knew. Soon a large horde of traitor forces commanded by the Word Bearers Commander Morpal Cxir encircled the palace and launched an attack against the valiant defenders. In the meantime, the Magos attempted to reactivate the data-engine and establish comms with the orbiting fleet. Captain Ventanus knew their forces could not hope to repel the attacks indefinitely. The Word Bearers used the vast hordes of Chaos cultists as human fodder, driving them forward as they protected themselves from any significant counterattack. Terrible carnage was inflicted upon the defenders by packs of horrific daemons as they punched through any breaks within the defensive line. As the assault grew more fierce, the defenders prepared to sell their lives dearly, but they were spared from their fate by the timely arrival of the 4th Company and its heavy armour support. The reinforcements bolstered the defenders resolve as they tore into the ranks of the traitors and decimated their ranks. Vetanus knew that although they were strong in spirit and well-armed, it was only a matter of hours before the defender’s position would be overrun and everyone was slaughtered.

Despite the brutality of the traitor assault, Tawren focused on her duties and managed to reactivate the dormant data-engine. With it, she was able to gather a clearer picture of the situation’s totality, especially the truly catastrophic scale of the losses: the enormous death toll, the crippling wound to the XIII Legion, the decimated and burning cities, slaughtered populations, the devastated geography from the fallen debris and the systematic annihilation of the Ultramarines’ fleet. Ventanus finally managed to get into contact with Primarch Guilliman to give him a clearer picture of the resistance across Calth. Though broken and scattered, it was fierce. Spread across hundreds of locations, as many as 30,000 Ultramarines battle-brothers and 200,000 Imperial Army and Mechanicum warriors were still active. Coordinated, they could achieve more than if they remained uncoordinated. Only the Ultarmarines’ dogged determination kept them going. In any other circumstances, Calth would have been declared lost, but the XIII’s fierce resolve prevented them from giving into despair.

A Desperate Gambit
Fortunately, amidst all this negative information, somehow Magos Tawren managed to discover a killcode that her former mentor Hesst had hidden within a secure data-engine which had then been closed off and sealed. This data-engine was the manifest cogitator of the cargo handling guild, located in a secured bunker in the industrial zone between Numinus Starport and Lanshear landing grounds. This data-engine was responsible for running cargo operations for both parts, and thus was more than powerful enough to manage the dataload of the planetary weapons grid. As a civilian engine, it was not a primary military target, therefore Hesst was able to take advantage of this. Though he suffered from the painful overload of the data-shock that was killing him, Hesst had managed to clean this data-engine with his killcode and then shut it away. Contacting Guilliman aboard the Macragge’s Honour, Ventanus apprised his Primarch of the new developments. He informed him that the enemy was controlling the weapons grid using a captured data-engine on one of the surviving orbital platforms. Tawren would be able to purge the system, but could not override the control. They would need fleet assistance in order to target the platform.

A practical had to be decided on what would the plan of attack be. Shipmaster Hommed recommended a ranged bombardment: primary spinals, lances. The Macragge’s Honour certainly possessed the firepower. Chapter Master Marius Gage seconded the suggestion. But if they didn’t make a direct kill with the first salvo, there was a real danger that the enemy would retaliate with the defence grid and finish the flagship. Chapter Master Klord Empion of the 9th Chapter opted for a close attack: flagship power to yield, shields up, throw off the enemy cruisers surrounding them and go for the yard and blow it out of nearspace. Ram it, if necessary. Except, the moment they moved, the moment they even rated a power condition, the Macragge’s Honour would become a target. The flagship could move rapidly, and with devastating effect, but not faster than the weapons grid, and that was supposing nothing got in their way, like a drive issue, or an enemy ship. Therefore, Empion’s plan was also dismissed. Finally, Chapter Master Gage’s alternative plan was considered: put all available power into the teleport system and transfer a kill squad, possibly two if the power lasted, direct to the Zesun Verid Yard. It was agreed.

Led by Guilliman himself, the first kill squad of 50 Ultramarines assembled in the flagship’s teleportation terminal. The transverse assembly deck was their chosen teleport destination. It was the largest interior space, and thus allowed for the greatest transfer imprecision. Their assault target was the yard’s master control room, two decks up. Given the risk factor and the atrocious error margins, the teleport was considered a success. 46 members of the kill squad appeared with Guilliman on the transverse assembly deck of Zetsun Verid Yard. They had lost 4 during transition.

The kill squad encountered heavy resistance from the Word Bearers, but with their Primarch Guilliman at the fore, the enemy forces baulked as the angry Primarch surged forth to kill them. With righteous fury he killed over a dozen Word Bearers, including those of the vaunted Gal Vorbak. Though they lost 8 Ultramarines, the kill squad managed to break through into the master control room. A heavy barrage of bolter fire greeted them. The real fight awaited them. Within its chambers Kor Phaeron, Black Cardinal and Master of the Faith, ordered his men forward. Then he flew at Guilliman, summoning forth fell black energies torn from the very pits of the warp. Guilliman roared his challenge and charged forth.

Final Assault
Simultaneously, the 4th Company struck along the Ketar Transit, a main access that linked the container stores to the northern facilities of Lanshear port. Their target was the data-engine of the cargo handling guild located in the bunker system below the majestic prospect of the guildhall. Ventanus lead the foot advance across the broken streets himself, behind a column of Land Raiders. Word Bearers rose up to block the main charge. Instead of overwhelming the Loyalist forces with well-directed firepower which might have broken or turned Ventanus’s charge, the Word Bearers simply waited for the inevitable clash of close combat. They relished the prospect of testing their occult blades against the vaunted XIII in hand-to-hand combat. The traitors wanted to prove themselves against the paradigms to which they had been compared to so many times. The charging cobalt-blue warriors of the Ultramarines charge into the solid red line of the Word Bearers. The fighting was both brutal and unforgiving with neither side asking for quarter nor expecting any in return.

Reaching the guildhall, Ventanus lept the barricades, leading the assault forward. He tore into the fleeing cultists who shrieked in fear at the prospect of facing the fierce Loyalist Captain. As the Ultramarines moved forward into the building they continued to be pounded by enemy artillery and heavy weapons. Reaching the precious data-engine, Magos Tawren attempted to connect into it and upload the kill code. As the Magos concentrated on gaining access to the defence grid, their fate took a turn for the worst. The forces of Hol Beloth descended upon the guildhall with a vengeance. He was coming to punish the upstart Ultramarines. He was coming with Titans and Terminator armoured cataphractii and the dreaded Gal Vorbak.

On the surface, the situation looked grim. Enemy Titans continued to fire upon the guildhall shaking it to its very foundations. Ventanus checked with Tarwen for a status update, but progress was slow as the Magos attempted to connect with the server. The situation outside was rapidly deteriorating as armour columns loyal to the Word Bearers move into position and began firing at the Loyalists with a hail of shells and bulk las. Two Reaver-class Titans approached at full stride, intent on annihilating the Loyalist forces. With the majority of the ally commanders dead, Ventanus knew that his company line was all but broken. The 4th had done all that they could do, for it could not match the overwhelming strength of Hol Beloth’s offensive. The weapons fire intensified as the Titans continued to pound the guildhall. The Magos finally managed to launch the kill code so that she could prepare to purge the system and wrest control back of the defense grid. But until control of the grid was taken away from the enemy there was nothing that she could do.

The Titans moved closer to their position. The last Shadowsword remaining with the 4th fired and damaged one of the striding giants, but the pair of Titans returned fire in unison, destroying the super-heavy tank in a vast conflagration. Ventanus knew in his hearts that nothing else was coming to support their efforts. There were no more reinforcements. All hope was as good as lost and their attempts were all for naught. The XVII Legion had won the Battle of Calth.

Turning Back From the Brink
Within the master control room of the Zetsun Verid, Guilliman confronted Kor Phaeron. Instead of fighting the Primarch in honourable combat, he resorted to using his malefic abilities granted by the Chaos Gods, slamming the XIII Primarch against the chamber wall with a column of wretched darkness that burst from the palm of his right hand. Though shaken, the Primarch rose to his feet to face his attacker. Guilliman charged him again but was slammed back into a bulkhead with another powerful dark beam of eldritch power. Guilliman attempted to stand, staggered, then fell. He then half rose and clenched his power fist. The force of the Black Cardinal’s blow was so vicious that the ceramite of the Primarch’s breastplate was cracked. Guilliman coughed and blood dripped from his mouth. He attempted to stand once more.

Kor Phaeron blasted him again, this time with a strange negative electrical charge around Guilliman that caused him to seize in a violent fit. The Primarch is left on his hands and knees, his whole form smouldering, and his head bowed. The Word Bearer drew his athame and stepped forward, the Primarch’s fate in his hands. He has the opportunity to end the life of the great Primarch or, with his own hand, he can turn him to the Warmaster’s cause. Just as Erebus had turned the Warmaster, so too, would Kor Phaeron achieve the impossible. Knowing that the Primarch was hurt, weak and vulnerable, one cut of the athame would free Guilliman’s sanity whilst Kor Phaeron took advantage of his weakened state, and sliced away his inhibitions. With one burning cut of his fell blade he would reveal to Guilliman the Primordial Truth. It would be so much more fitting to return to the court of Lorgar and Horus Lupercal with Guilliman as a willing and pliant ally.

The vile Word Bearer stepped forth beside the wounded Primarch and put the blade of the athame to Guilliman’s throat. The Primarch grunted through clenched teeth as the athame bit. Kor Phaeron attempted to cajole Guilliman into giving up and joining their blessed cause against the ‘False Emperor’. Guilliman only muttered in reply. With every single word an effort, the Primarch explained to the Black Cardinal that he had made a grave error, for he had chosen the wrong practical: toy with him or kill him. He had made the wrong choice. The arrogant Word Bearer merely smiled, confident in his inevitable triumph over the Ultramarines Primarch. Guilliman made Kor Phaeron pay for his hubris. Though its power had long since shorted out and failed, he buried his armoured claw in the Black Cardinal’s chest and ripped out one of his black hearts. As one of the Ultramarines Sergeants rushed to the wounded Primarch’s aid, he ordered the Sergeant to forget about him for the moment and to kill the system. Unable to figure out how to shut down the data-engine, Guilliman ordered the Sergeant to shoot it. But the Sergeant was out of ammo, and so, he used his Power Sword instead.

On Calth’s surface, the remnants of the 4th Company prepared to face their inevitable doom, defiant to the very end. The bunker 300 metres below the guildhall trembled as it was continuously struck by devastating salvos of enemy fire. Suddenly, Magos Tawren informed her Ultramarines allies that their circumstances had drastically changed – what appeared to be two Loyalist Titans had vectored into the fight. One of them had already made an engine-kill against one of the Word Bearers-aligned Titans. Reinforcements had arrived to supplement the beleaguered 4th Company. The reinforcement strength exploded into the Lanshear Belt from the east, fast and mobile. One of the four Tetrarchs of Ultramar, Eikos Lamiad, the Primarch’s Champion lead a ragged host of soldiery collected from the desert and the burning hills around the Holophusikon.

A column of Land Raiders and armour supported by three Titans: two Reavers and a Warlord-class Titan. An infantry force followed, moving rapidly. She identified them by insignia, heraldry, trace codes and unit marker transponders. The force was mostly XIII and Mechanicum elements from Barrtor and the Sharud muster, but there were 20,000 Imperial Army troopers as well, bringing lighter armour and support weapons. The relief force formed two prongs of assault. One was a Legion force led by a Sergeant of the 112th called Anchise, and a Captain of the 19th called Aethon. The other was predominantly Army, and was commanded by a Colonel of the Neride 41st called Bartol, but it was physically being led by Eikos Lamiad and a lumbering Ultramarines Contemptor Pattern Dreadnought.

Hol Beloth’s forces flinched at the unbridled force of the attack, not just the firepower, but the coordinated strength of it. The shattered survivors of the XIII Legion should not have been able to organise with such precision and effect. In the midst of such chaos, confusion and a world ablaze, they should not have been able to rally and focus around such a strategically specific point. The assembled survivors of the Calth Atrocity expressed their fury and their vengeance against the traitrous bastards of the XVII Legion, inflicting massive damage upon the enemy. Despite their efforts, Tawren still had no grid control with which to shift the combat dynamic. She had the killcode, but no control.

Without warning, the control codes suddenly released. The Magos observed the digital sequence suddenly shift across the noospherics: [Control Suspended (engine failure)]. She doesn’t hesitate in her final and most important duty, running the killcode directly into the suddenly open system. It quickly burned through the corrupted numerics of the Octed scrapcode, and she is able to take control of the defence grid. She selected the discretionary mode and used the orbital defence platforms to launch a devastating weapon strike upon the Lanshear port. Server Tawren addressed the XIII Legion and all those allied with them to brace for impact. Coming straight out of the sky, a column of deadly vertical light struck the city-zone around the guildhall in the northern depot area. It obliterated the enemy Titans, armoured vehicles and reduced the cult auxiliaries and Word Bearers formation to so much ash. The weapon strike was ‘dangerous-close’, in some cases less than half a kilometre from where the Loyalists took shelter from the impact sites. The Ultramarines and Imperial Army forces were untouched, though their eardrums burst and they suffered radiation burns to any exposed skin. Hot ash plastered the rain-soaked power armour of the Space Marines, covering them all with the remnants of their former Word Bearers enemies. Ironically, the Ultramarines ash-covered armour appeared a gun metal grey, the old livery of the XVII Legion.

Her task uncompleted, the Magos redeployed the grid elements available to her, hitting other surface targets. Simultaneously, she re-tasked the orbital platforms and began to systematically exact punishment upon the Word Bearers fleet. Since the first cataclysmic orbital strike, it was now the crimson-hulled warships of the XVII Legion that were annihilated. The dynamic of the entire battle had finally shifted in the Ultramarines favour.

Meanwhile, Guilliman and his kill squad attempted to extract themselves from the burning master control room. The flames and smoke rapidly filled the habitats of the Zetsun Verid Yard. The remainder of the kill squad retreat rapidly, packed tightly around their wounded, limping Primarch. As they awaited transport from the inbound flagship, the Primarch looked out one of the viewports and is stricken by what he observed. Though they had won something, they had only managed to accomplished it just in time to lose everything. He and his men saw the Veridian star that had been fired upon by the usurped defence grid. The baleful light of the stricken star looked as if it was preparing to go supernova, which would wipe out all life upon the surface of Calth.

Suddenly the Primarch’s attention was diverted when he looked below their position and saw half a dozen surviving Word Bearers carrying the bloody carcass of Kor Phaeron. Somehow, the wretched Black Cardinal had somehow remained alive despite the fact that Guilliman had tore out his primary heart. Drawing their boltguns, the Ultramarines fired upon the retreating Word Bearers, just as their forms shimmered and vanished in a blink of teleport energy.

Guilliman contacted Chapter Master Gage aboard the Macragge’s Honour, and ordered him to hunt down the Infidus Imperator at all costs. He did not want the Master of the Faith to escape his ultimate fate. Though worried about his Primarch’s well-being, Guilliman informed the Chapter Master that they would secure one of the Ultramarines vessels docked there. The Word Bearers grand cruiser Infidus Imperator turned in the debris-rich belt of Calth nearspace, ships dying in flames behind it. It engaged its drive and began a long, hard burn towards the outsystem reaches. As it accelerated away, the Macragge’s Honour turned in pursuit, beginning of one of the most infamous naval duels in Imperial history.

Aftermath
When the Word Bearers utilising the orbital platforms to deadly effect against Calth’s sun, it boiled away its surface and threatened to send it supernova.

Some of the ships slain during the Calth Atrocity will continue to circle the tortured star for a hundred thousand years as frozen wrecks, as tomb ships for the silent dead, mummified and preserved in the act of screaming their final screams.

Source

 * Horus Heresy: Collected Visions, pp. 153, 158, 162-164
 * Know No Fear (Novel) by Dan Abnett