Perturabo

Perturabo, sometimes called the Lord of Iron, is the Primarch of the Iron Warriors Traitor Legion, one of the original twenty Space Marine Legions. He and his IV Legion sided with Chaos during the Horus Heresy and he has since ascended to Daemon Prince status. Perturabo, like his Iron Warriors, had a natural affinity towards the intensive use of technology in combat and a cold, emotionless logic when dealing with others, but he lacked faith in either the Emperor or the Chaos Gods to whom he later swore his soul. Perturabo was a master of siege warfare, considered the most skilled in this area of all the Primarchs. His greatest rival amongst the other Primarchs was Rogal Dorn of the Imperial Fists, who was believed to be the greatest builder of siege defences in the Imperium. Perturabo currently resides within the Eye of Terror on the Daemon World of Medrengard.

Origins
When the Primarchs were scattered to the ends of the galaxy from the Emperor's gene-laboratory beneath the Himalazian (Himalayan) Mountains on Terra by the Chaos Gods, Perturabo landed on a Civilised World named Olympia. Perturabo grew up on the mountainous planet divided into constantly warring city-states. He was discovered climbing the mountains below the Olympian city-state of Lochos. The city guards, having realised this was no ordinary child, brought him before Dammekos, the ruling Tyrant of Lochos. Dammekos was intrigued by the strange child and brought him into his household and treated him as part of his family. Supposedly, Perturabo never fully accepted his lot, never truly trusting the Olympians and refused to return any affection given by his adopted father. Dammekos spent plenty of time with his new son, but never received any affection in return.

There was a mysterious explanation for Perturabo’s inherent mistrust, unknown to anyone but himself. Upon reaching the summit after climbing the rain-slick cliff, the exhausted youth had peered towards the heavens and gazed upon a strange star maelstrom. When he inquired to the Tyrant’s guards whether they could see the strange phenomenon that the young Primarch saw, the bewildered guards replied that they were unable to. For the rest of Perturabo’s life, this star maelstrom would continue to look down upon the Primarch; judging and measuring his worth and spying on his every movement. A life lived beneath its cold scrutiny made him brooding and loath to offer his trust, ever-watchful and aware of its baleful glare. It would be over two centuries later before he found a reason to venture into this strange star maelstrom’s mercurial depths, a galactic phenomena whose name he would one coin, a name that would one day strike fear into the hearts of all those that heard it. This star maelstrom would one day be known as the Eye of Terror.

Many Olympians saw Perturabo as a particularly cold and brooding child, though the fact that he was a genetically engineered superhuman who had been mysteriously thrown onto a far-off world with no idea of his origins or purpose was certainly not conducive to the development of a trusting nature. Despite his aloof demeanour, Perturabo learned from the culture in which he found himself the arts of the siege, for Olympia’s myriad warring city-states afforded plenty of opportunity to study both the theory and the practise of this highly specialised branch of warfare.

When the Emperor of Mankind arrived on Olympia as part of the Great Crusade and informed Perturabo of his place in the wider galaxy. After his discovery, the young Primarch was brought to Terra, to learn from his father about his chosen destiny and to meet some of his brother Primarchs. During his studies, Perturabo learned of the of the Firenzii and searched the ruins of Old Earth for copies of his surviving journals, gathering his hidden papers and learning of the works he pursued in private. Perturabo and his brother Magnus of the Thousand Sons Legion spent many months together in search of buried secrets of the past glories swept away in the chaos of Old Night. It’s true, though it was the esoteric writings of the world’s former masters that most interested him. He cared more for the ancient philosophies of the lost civilisations than its mechanical wonders, but it was a heady time of exploration for both Primarchs. Perturabo got along well with his brother Magnus, for both Primarchs shared a love of learning, and a hunger to know new things. Perturabo was not a Primarch to whom the natural ebb and flow of friendship came easily. No, his friendship was not easily achieved, but his loyalty, once won, was as unbreakable as the hardest iron. Or so he had thought, until time and taking the metal to the stone again and again would show him that even the hardest iron could break if worn thin enough.

Oath of Moment
When the appointed time came, and the Emperor was ready to send his son back out into the galaxy to help with the galactic conquest known as the Great Crusade to reunite the disparate tribes of man and bring them into the Imperial fold, Perturabo, like his fellow Primarchs before him, ascended to the crenellated peak of the Astartes Tower to swear his oath of moment. He made the long ascent upwards to the polished marble spire, the night before leaving Terra for a life of war. Each step required a superhuman effort of will, determination and courage. It was no simple screw-stair, but a challenge to the heart and intellect, a psychic communion with the Emperor himself that tested the very boundaries of a warrior’s endurance.

Perturabo pledged his devotion to the fledgling Imperium, and assumed the mantle of Primarch and commander of the IV Space Marine Legion, whom he renamed the Iron Warriors. According to established practise, the Primarch was declared lord of the world on which he had been raised, effectively deposing his adoptive father, the Tyrant of Lochus, as the most powerful ruler on the world. Given command of the IV Legion which had been created from his own genome, Perturabo order the Iron Warriors to begin the process of inducting new recruits from the most able candidates amongst the peoples of Olympia. Dammekos is said to have spent his remaining few years gathering forces to attempt to retake his power and overthrow Perturabo and the Imperium's rule. Dammekos failed in these efforts at rebellion, but created a current of anti-Imperial political unrest among the people of Olympia which would come to haunt Perturabo and his Iron Warriors later.

Great Crusade
After his submission to the Emperor, Perturabo led his Iron Warriors in their first operation of the Great Crusade under his command: a lightning assault against the world of Justice Rock which lay near to Olympia and its ruling Black Judges, bringing the world into Imperial Compliance. The Iron Warriors went on to erect citadels throughout the regions of the galaxy they fought in and conquered for the Imperium. Small numbers of Iron Warriors were left behind at these outposts to serve as Imperial garrisons at the command of the Emperor, but Perturabo resented being forced to split his Legion, unlike the other Primarchs' forces. As time went on, the Iron Warriors found themselves stereotyped within the Imperium, even by other Space Marine Legions, as being the best Imperial force for undertaking sieges and garrison duty, but eventually the Iron Warriors were so worn out and frustrated by the constant grinding slaughter of siege warfare that they simply began to enjoy the killing they had to do when a besieged opponent refused to surrender. The Iron Warriors proved themselves amongst the most able siege troops in the Emperor’s armies. Perturabo was possessed of a keen, cold, and calculating mind well-suited to the highly technical aspects of such a style of warfare. Furthermore, he was gifted with an affinity with technology, and able to debate the finer points of the most esoteric arts with the highest placed adepts of the Mechanicum. The Iron Warriors received cross training on Mars, further refining the specialisation, until only the Imperial Fists of Rogal Dorn could equal their expertise. World after world that rejected the new future for Mankind vested in the Imperial Truth espoused by the Emperor’s Iterators capitulated when confronted with the prospect of a protracted siege by the Iron Warriors, and countless worlds were brought to Imperial Compliance that would otherwise have been devastated in bitter, and ultimately pointless wars if not for the IV Legion's brutal reputation. There are apocryphal accounts that it might well have been the Warmaster Horus who kept the IV Legion in this role in the last days of the Great Crusade. Horus knew that the strains and frustrations engendered by constant siege warfare would allow him to more easily sway the mind of Perturabo towards Chaos as the Iron Warriors' Primarch grew increasingly resentful of his Legion's assigned duties.

It is widely acclaimed in Imperial legend that Perturabo was greatly envious of Rogal Dorn, the Primarch of the Imperial Fists Legion. Perturabo was annoyed by Dorn's constant reminders of the perfection of the defences created by the Imperial Fists for the Imperial Palace on Terra at the Emperor's command. The other Primarchs also kept Perturabo at an emotional distance. This coolness on their part might have been because of Perturabo's supreme command of his Legion's technology and siege tactics, far in advance of anything the other Primarchs were comfortable with or able to emulate with their own forces.

Perturabo is referred to as the "comrade" who devised the best plan to avoid the defences of Overdogg Mashogg, an Ork Warboss under attack by Leman Russ, Primarch of the Space Wolves, and Jaghatai Khan, Primarch and Khan of the White Scars. Yet Perturabo appears to have grown ever more resentful of his role during the course of the Great Crusade, and perhaps in an effort to prove his superiority over Dorn and his other brother Primarchs, he accepted ever more arduous planetary siege and assault missions on behalf of his Legion. Another prime example is the Compliance of the Araaki Spiral, a joint Imperial Compliance campaign conducted by the Iron Warriors, Imperial Fists, Dark Angels and White Scars Legions in a region of space known as the Araaki Spiral. The Araakites were well-versed in the art of building fortresses, and their strongholds were dug deep around narrow passes, remote hilltops and natural barriers in the landscape. Once again, the Iron Warriors were sent to a resistant star system to conduct brutal siege-warfare against formidable fortress-builders. The Araakites knew their craft well and the campaign to take their world for the Imperium proved both bitter and hostile. It would take many years for the IV Legion to regain its former strength from the losses sustained during the drawn-out war of attrition that it’s Astartes suffered in the Araaki Spiral.

In the wake of the inevitable Imperial victory, great works of art and heroic verse were composed, celebrating the courage of the other Space Marine Legions, but nowhere in the reams of poetry and artwork were the grim labours of the Iron Warriors judged worthy of note. Only in a predella to a larger work painted by a notable Imperial artisan were the warriors of the IV Legion displayed; illustrating a lone Iron Warriors Apothecary removing the gene-seed of a dying Iron Warriors Legionary as the flag of the IV Legion's greatest rivals, the Imperial Fists, flew over a captured fortress. Perturabo sought out the artist to procure the piece for himself, only to have it put it to the torch once he had done so. If his sons would not be honoured properly, he told the horrified artist, than they would not be a part of a record that glorified another. Afterwards, Rogal Dorn had offered a rich commission for the artist to repaint the predella, but the artisan wisely refused.

Worlds considered by others as unbreakable were cracked open by the methodical application of the Iron Warriors' overwhelming force, yet this approach to war took a remorseless toll even on the superhuman Space Marines. Gruelling preparation culminated in brief but extreme violence, and soon the Iron Warriors came to prefer a besieged defender to defy them rather than to surrender, so that the pent-up pressure of siege warfare could be released in the moment of the foe's total defeat. To make matters worse, the Iron Warriors came to be utilised as elite garrison troops, with small forces detached from the IV Legion and tasked with guarding the worlds they had worked so hard to bring to Compliance. While other Primarchs refused point-blank to see their Legions used in such a way, believing that garrison work was the task of the Imperial Army, Perturabo acceded to the duty, though with an increasing and notable lack of grace.

Horus Heresy
As the tragic outbreak of the Horus Heresy grew closer, it appears that Perturabo was put under ever increasing pressure, and as a result the fires of his bitterness were stoked to a raging inferno. Some Imperial historians have postulated that it was Horus himself who, time after time, engineered events and adjusted deployments to the detriment of Perturabo's psyche. Whatever the truth, events came to a head when, leading his Iron Warriors on a campaign to cleanse the Hrud Warrens on the world of Gugann, the Primarch received news that his own homeworld, Olympia, had rose up in rebellion against the Imperium. Though Dammekos was long dead, the other Olympian demagogues had brought the people together and risen in arms against the rule of the Emperor of Mankind. The thought of being the only Primarch who could not control his own Legion's homeworld appalled Perturabo.

Perturabo and the IV Legion returned to their homeworld and brutally purged Olympia of its rebels city by city, overrunning the fortresses he had built and sparing no one who stood against him. By the time the massacre was over, five million Olympians had been killed and the rest put into vicious slavery to the Iron Warriors. Perturabo looked on at the remains of his homeworld in cold silence. Only once the great world pyres were burning to cleanse the world of the heaps of corpses created by the IV Legion's assault did Perturabo fully realise what he had done. The Iron Warriors were no longer the saviours of the Imperium; they had been destroying the alien Hrud one moment and yet, in the next, they were committing genocide against their own people. With the cooling of Olympia’s mass pyres had come the realisation that nothing the Lord of Iron could ever do from that moment could ever atone for a worldwide genocide. His father would never forgive him so grievous a sin, but Horus had not only forgiven it, he had lauded his brother’s thoroughness and dedication. Horus had sworn Perturabo never to feel guilt over what he had done to Olympia, but that was an oath easier to make than to live by.

It was at this time that disturbing news of the outbreak of the Horus Heresy on the world of Istvaan III reached Olympia and new orders for the Iron Warriors came from Terra. Leman Russ and the Space Wolves had attacked Magnus the Red and his Thousand Sons Legion on their homeworld of Prospero at the direction of the Emperor. Horus had turned Traitor with his XVI Legion, the Sons of Horus, alongside some other Legions such as the Death Guard, Emperor's Children and the World Eaters. The whole of the Imperium was on the brink of an outright civil war. The new orders from the Emperor ordered the Iron Warriors to join with six other Loyalist Space Marine Legions to face Horus and his Traitor Legions on the world of Istvaan V. During the battle that followed the Iron Warriors, Night Lords, Word Bearers and Alpha Legion all went over to the side of Horus and almost completely destroyed the three remaining Loyalist Legions of the Imperial assault force -- the Iron Hands, the Salamanders and the Raven Guard -- at the infamous Drop Site Massacre on that world.

In the wake of the Drop Site Massacre, Horus presented Perturabo with a Power Hammer called Forgebreaker that had been the personal weapon of the Loyalist Primarch Ferrus Manus of the Iron Hands, who the Traitor Primarch Fulgrim had beheaded during the Drop Site Massacre. The granting of this boon was the embodiment of a new pact between the Warmaster and the Iron Warriors' Primarch, a gift from Horus to Perturabo intended to symbolise Perturabo and the Iron Warriors' newfound allegiance to the Warmaster rather than the Emperor. Fools claimed that Forgebreaker had sealed the pact between the Warmaster and the Iron Warriors, but only Perturabo knew it was forgiveness that bound the Iron Warriors to Horus Lupercal.

Hyrdra Cordatus
As Horus’s rebellion grinds on the Iron Warriors take the time to humble their great enemies, the Sons of Dorn, upon the isolated world of Hydra Cordatus. The Iron Warriors made planetfall in the wake of a saturation bombardment that reduced the valley where the planet's lone formidable fortress, known as the Cadmean Citadel, was situated and the agri-settlements filling its fertile deltas to ash. Magma bombs and mass drivers boiled away the rivers and reduced fecund earth to arid dust. The Cadmean Citadel was left untouched, and small garrison of Imperial Fists Legionaries still found it difficult to believe that such a precise bombardment was possible. But the Iron Warriors had purposely done this in order to show the Imperial Fists that they were superior to them in every way. The technological cunning of the ancient fortress builders, married to the artfully wrought geography and the courage of the defenders, proceeded to keep the Iron Warriors at bay for almost three months. Every day the Loyalist warriors stayed alive, it kept the enemy from redeploying and bringing their strength to bear elsewhere against the forces of the Imperium. Yet, when the Iron Warriors finally overcame the citadel’s ancient defences and broke open its walls they ran amok. They slaughtered the remaining Imperial Fists Legionaries, the heroic men and women of Hyrdra Cordatus that had chosen to stand with them, and the refugees from the devastated fields below the fortress. Fifty-two Imperial Fists and thirteen thousand men, women and children were crammed within the citadel’s walls. When the final assault came, the Lord of Iron himself spearheaded the audacious attack upon the citadel's defenders, and slaughtered over thirty Imperial Fists Astartes himself in a span of only a few minutes. The rest of the Cadmean Citadel's defenders were slaughtered to a man and the surviving refugees were enslaved by the Iron Warriors before they moved on to their next objective. Hydra Cordatus was reduced to a barren desert world by the Traitor Legion's assault.

The Angel Exterminatus
Following their victory, word reached the Lord of Iron that Fulgrim, Primarch of the Emperor's Children wished to rendezvous with him to discuss something of great import. Though the Phoenecian had yet to reveal the true purpose of his visit he had been promised that is was "wondrous." Perturabo knew that his brother had a flair for the overdramatic, which only seemed to have gotten worse since the III Legion threw their lot with the Warmaster. The Lord of Iron counted none of his fellow primarchs as close, but the Phoenician’s adherence to perfection in all things had once provided common ground between the two super-warriors and allowed them to talk as trusted comrades-in-arms if not beloved brothers. What the Emperor’s Children had sought with constant motion towards the attainment of perfection, the Iron Warriors earned with rigid discipline and methodical planning; two divergent paths to the same ultimate goal.

Perturabo believed Fulgrim's visit had something to do with Mars. The Warmaster needed the Martian theatre fully secured before they moved against Terra, and he believed that Fulgrim was there to seek the Iron Warriors aid in breaking open the forge temples of the Adeptus Mechanicus. If he was right, he wanted his Legion to have a plan in place to achieve that objective. Until the Iron Warriors received further orders, Perturabo would humour his brother and listen to what Fulgrim had to say. While making plans for the upcoming campaign, Perturabo received word that the Emperor's Children had arrived, unannounced, on the surface of Hydra Cordatus. Over three hundred drop-craft had landed beyond the mouth of the valley of the Iron Warriors location.

The IV Legion quickly gathered in formation to honour the III Legion with a vanguard to receive them. Battalions of Thorakitai Imperial Army troops stood ranked in their tens of thousands. Before them stood two hundred Grand Battalions of Iron Warriors, fifty thousand warriors in amberdust-burnished warplate. Such a display of might and magnificence had not been seen since the slaughter unleashed upon the black sands of Istvaan V. Perturabo and his senior officers looked on in awe at the gaudy cavalcade of noise, colour and spectacle that proceeded from their drop site into the valley. Fulgrim and his Emperor’s Children were now completely unrecognizable from the honourable warriors that once formed the III Legion. Perturabo knew something fundamental had changed within the Emperor’s Children, but could not imagine what purpose the disfigurements and degradations its warriors now sported could possibly serve.

Fulgrim met with his brother Primarch in the private inner sanctum of his command bunker with an enticing offer that Perturabo couldn't refuse; the means to make it so that the Lord of Iron's every desire could be made real and would never disappoint, never fail to live up to his fondest expectations, and never, ever be eclipsed. Fulgrim came with an offer to unite their mutual forces in battle on a glorious quest. One that might tip the balance of the Warmaster’s rebellion. Though Perturabo was suspicious of his brother's intentions, perhaps this joint venture would grant understanding through common cause. Fulgrim revealed his purpose; they were to venture to the warp storm that had plagued Perturabo's dreams all of his life. Within, was hidden a cache of ancient and forbidden xenos weapon known as the Angel Exterminatus. It had been hidden in the grave of its doom, a weapon of such power that the stars themselves turned upon it rather than allow it to escape its prison.

The Eye of Terror
"A name to lodge in the hearts of all who hear it."

- Primarch Perturabo, after permanently coining the name for the Eye of Terror on the stellar astropathic charts.

For as long as he remembered, no matter how many thousands of light years separated him from this particular warp storm, Perturabo was always aware of its presence and could perceive an echo of it on every world where he had looked to the heavens. He didn’t know whether this warp sight had been engineered into his perceptive apparatus deliberately, like Sanguinius’s wings or Corax’s eyes, or was simply a quirk of his genetic code, but it had been a blessing and a curse since his earliest memories. The storm haunted his dreams, threaded his nightmares and coloured his every thought since he had learned something of its nature. He’d once asked the Iron Hands Primarch Ferrus Manus whether his silver eyes allowed similar insight, but his brother had just shaken his head and given him a look of faint scorn, as though he had just admitted to some secret weakness or vice. He had never mentioned it again.

When the joint fleet arrived to the outskirts of the star maelstrom, for once in his life, Perturabo looked upon it and knew that others could see it too. They did not see it quite as he saw it, but they could at least acknowledge its existence. He saw beyond its dark light to the engulfed worlds within: phantom images that ghosted in and out of perception and fleeting moments of solidity in a realm where such things were anathema. He saw planets where all reason and Euclidian certainty had been abandoned, where the physical laws that underpinned the galaxy were playthings of lunatic forces beyond mortal comprehension. And now he was to venture into its depths, following the guidance of an alien seer. What would he find in there and, more to the point, what might find him?

Before entering the star maelstrom, Perturabo called up the astrogation charts of this region of space, reading the flickering key labels for those few stellar objects in this region worthy of a name. At the heart of the holographic overlaid, a vertical black label bisected the fiery orange heart of the star maelstrom. Imposed upon the bar was the name Cygnus X-1. Perturabo knew the star maelstrom was not the first spatial anomaly to bear that name, and whichever lowly scribe had ascribed it again was a fool. Something this powerful and terrible deserved a name to strike fear into the hearts of all who saw it, a name that would resonate down the millennia until the end of time, when the stars went out and the only light in the universe was the nightmare glow of the star maelstrom’s ever-devouring borders. Perturabo’s fingers danced over the slate from which the charts had been brought forth, and the name in the vertical black bar changed. It would change throughout the fleets, spreading to any data engine that called up maps of the galactic northwest. It was a name to lodge in the hearts of all who heart it -- The Eye of Terror.

The Sisypheum
Unknown to both the Iron Warriors and the Emperor's Children, they were being pursued by a ragtag group of survivors from the Drop Site Massacre of Istvaan V that were determined to stop them at all costs. These loyalists Space Marines were gathered from the scraps that had fought their way out of the killing ground of the Urgall Depression. They had managed to escape aboard an Iron Hands Strike Cruiser known as Sisypheum. Iron Hands and their mortal serfs formed the bulk of the crew, for most legionaries attempted to reach their own craft, but warriors of the Salamanders and a single Raven Guard were counted among its number. In the wake of the slaughter, escape from the Istvaan System had been a nerve shredding series of mad dashes under fire and silent runs through the traitor blockade, culminating in a final sprint to the gravipause, the minimum safe distance between a star’s mass and a vessel’s ability to survive a warp jump. The Sisypheum had escaped the trap, but not without great cost.

The months that followed saw the Sisypheum embark on a series of hit-and-run attacks on traitor forces on the northern frontiers of the galaxy, wreaking harm like a lone predator swimming in a dark ocean. Traitor forces seeking flanking routes through Segmentum Obscurus were their prey; scout craft, cartographae ships, slow-moving supply hulks heavily laden with mortal troops, ammunition and weapons. Disruption and harassment were their main objectives until contact had been established with fellow survivors. Contact was established with disparate groups of loyalist forces that had escaped the massacre, and a stratagem of sorts agreed upon. With the X Legion too scattered to function in a traditional battlefield role, its surviving commanders found their own way to fight back: as the thorns in the flanks of the leviathan that distract it from the swordthrust to the vitals.

At Cavor Sarta, an Iron Hand known as Sabak Wayland and the lone Raven Guard survivor Nykona Sharrowkyn had captured an Unlingual Cipher Host -- one of the so-called "Kryptos" -- a hybrid abomination creature of the Dark Mechanicum that had previously kept the enemy’s code network a cryptographic impossibility to break. With the Kryptos, loyalist commanders were able to finally access the traitors’ coded communications. And with this knowledge, the Sisypheum's, Iron Hands' Captain Ulrach Branthan, had ordered the Sisypheum to make the circuitous journey to Hydra Cordatus and the meeting of the traitor Primarchs. Since learning of Fulgrim's intentions, the crew of the Sisypheum made their way towards the star maelstrom, guided by a mysterious Eldar guide, to thwart the traitor's plan to acquire the so-called Angel Exterminatus.

Lord of Iron Unleashed
After that terrible battle, the Iron Warriors were let loose on the Imperium as full devotees of Chaos and Perturabo relished the opportunity to fight in a way that did not rely on massive sieges and grinding trench warfare. Because of their widespread deployment throughout the galaxy, dozens of Iron Warriors Warsmiths (company commanders) took over Imperial planets and demanded tithes to support the Heresy. While one part of the IV Legion turned Olympia and its surrounding star systems into an empire of iron, a large contingent of the Iron Warriors accompanied Perturabo to Terra alongside the rest of the Traitor Legions in the climactic Battle of Terra where he supervised the bombardment and siege of the Emperor's Imperial Palace by the Forces of Chaos. Perturabo took a perverse pleasure in tearing down the defences set up by Rogal Dorn and his hated Imperial Fists. It cannot be known whether Dorn’s masterfully constructed defences would have proved the undoing of the Iron Warriors, for Horus was slain by the Emperor before the matter could be fully determined.

After that terrible battle, the Iron Warriors were let loose on the Imperium as full devotees of Chaos and Perturabo relished the opportunity to fight in a way that did not rely on massive sieges and grinding trench warfare. Because of their widespread deployment throughout the galaxy, dozens of Iron Warriors Warsmiths (company commanders) took over Imperial planets and demanded tithes to support the Heresy. While one part of the IV Legion turned Olympia and its surrounding star systems into an empire of iron, a large contingent of the Iron Warriors accompanied Perturabo to Terra alongside the rest of the Traitor Legions in the climactic Battle of Terra where he supervised the bombardment and siege of the Emperor's Imperial Palace by the Forces of Chaos. Perturabo took a perverse pleasure in tearing down the defences set up by Rogal Dorn and his hated Imperial Fists. It cannot be known whether Dorn’s masterfully constructed defences would have proved the undoing of the Iron Warriors, for Horus was slain by the Emperor before the matter could be fully determined.

Post-Heresy
After fleeing Terra along with the other Chaos Space Marine Traitor Legions following Horus' death, Perturabo took the opportunity to take vengeance on the Imperial Fists with a specially-designed trap on the world of Sebastus IV. The trap was known as the Eternal Fortress, a massive keep centred within twenty square miles of bunkers, towers, minefields, trenches, tank traps and redoubts that were intentionally shaped to look like an 8-pointed Star of Chaos. Upon hearing of the existence of this supposedly impregnable redoubt maintained by his Legion's hated rivals, Rogal Dorn publicly declared that he "would dig Perturabo out of his hole and bring him back to Terra in an iron cage".

Rogal Dorn expected an honourable battle, but this was not to be. Beginning by isolating the four companies of the Imperial Fists that arrived to do battle from their orbital support, Perturabo began to carefully divide his enemy and destroy them piecemeal. Some Imperial Fists managed to penetrate the defences and reach the centre of the Eternal Fortress, only to find there was no central keep - simply an open space watched by yet more defenses. The fortress was a decoy of no real value, surrounded by twenty miles of killing ground. By the sixth day of the siege, Imperial Fists Space Marines were fighting individually, without support, using the bodies of their own battle brothers for cover.

The siege of the Eternal Fortress, later referred to in Imperial histories simply as the battle of the Iron Cage, lasted for a further three weeks. Relief came in the form of Roboute Guilliman and his Ultramarines, who drove off the Iron Warriors, but the siege left Rogal Dorn a broken man and rendered the Imperial Fists Chapter unable to fight for nineteen standard years while they rebuilt their forces. The gene-seed of over 400 Imperial Fists was captured by the Iron Warriors in the Iron Cage and later sacrificed to the nefaruious purposes of the Dark Gods, an accomplishment for which Perturabo was elevated to the rank of Daemon Prince of Chaos Undivided by the rare acclamation of the Ruinous Powers.

Following this victory, the Iron Warriors fled to the Eye of Terror alongside their fellow Traitor Marines and secured a new Daemon World named Medrengard, crafting a terrible fortress world where his soldiers ruled in vast towers. Today, the Iron Warriors give their greatest loyalty to Perturabo for saving them from what they believe was an unwarranted sacrifice in the name of the False Emperor of Mankind.