Roboute Guilliman

"The warrior who acts out of honour cannot fail. His duty is honour itself. Even his death - if it is honourable - is a reward and can be no failure, for it has come through duty. Seek honour as you act, therefore, and you will know no fear."

- Primarch Roboute Guilliman

Roboute Guilliman, sometimes referred to as the Avenging Son, is the Primarch of the Ultramarines Space Marine Legion and its myriad subsequent Second Founding Successor Chapters. Guilliman is the Primarch who single-handedly reshaped the Imperium of Man after the Horus Heresy during the Reformation, taking the lead role in reforming the administrative and military apparatus of the Imperium following the internment of the Emperor of Mankind within the Golden Throne on Terra. Guilliman is perhaps best remembered for being the author of the Codex Astartes, a key volume that laid out the proper tactics and military organisation for the majority of Loyalist Space Marine Chapters now in existence. Roboute Guilliman is also one of the few Loyalist Primarchs still alive. Following the Horus Heresy, Guilliman and his Ultramarines met the Emperor's Children Traitor Legion and the Daemon Primarch Fulgrim upon the field of battle where Guilliman was poisoned by a wound to his neck made by his traitorous fellow Primarch's Chaos-tainted blades. The Primarch was put into temporal stasis on the verge of death and his body was placed upon the throne that lies in the Temple of Correction on the Ultramarines' homeworld of Macragge. Many pilgrims of the Imperial Cult travel across the galaxy every year to visit the temple and see the body of a Primarch, a blessed son of the God-Emperor himself. Some pilgrims claim that the grievous wound is slowly healing, though such an action should be physically impossible within an activated stasis field. Yet some believe that the Imperium and Mankind are entering the End Times and that the Emperor is using his divine will to enact a miracle and resurrect his son to serve as Mankind's champion in its most desperate hour.

Early Years
According to Imperial legend, the Emperor of Mankind created the Primarchs from artificially-engineered genes using his own genome as a template, carefully imbuing each of them with unique superhuman powers. Imperial doctrine goes on to tell how the Ruinous Powers of Chaos spirited away the Primarchs within their gestation capsules, scattering them widely across the galaxy through the Warp. More than one of the capsules was breached whilst it drifted through Warpspace - the forces of the Immaterium leaked in, wreaking havoc on the gestating being inside the capsule. Undoubtedly damage was done and Chaotic corruption affected several of the Primarchs, although the nature of that corruption would not become apparent until the Horus Heresy.

After drifting for decades, or in some cases even hundreds of years, the twenty gestation capsules came to rest on human-settled worlds throughout the Milky Way Galaxy - distant planets inhabited by a variety of human cultures. The capsule containing the developing form of one Primarch fell upon the world of Macragge in the Eastern Fringes of the galaxy. This was a bleak but not inhospitable world that Mankind had inhabited for many centuries since the Dark Age of Technology. Its industries had survived the Age of Strife and its people had continued to build sub-light spacecraft throughout the period of intense Warpstorms. The people of Macragge had successfully maintained contact with neighbouring human-settled star systems, despite the loss of many ships and crews. The Primarch's capsule was discovered by a group of noblemen out hunting in the forest. They broke the capsule's seal to reveal a strikingly beautiful and perfectly formed child surrounded by a glowing nimbus of innate power. The amazing infant was brought before Konor Guilliman, one of a pair of Consuls who governed the civilised region of Macragge. Konor adopted the child as his son and named him Roboute Guilliman.

The young Primarch grew quickly, and as he did so his unique physical and mental powers became obvious for all to see. By his 10th birthday he had studied and mastered everything the wisest men of Macragge could teach him. His insight into matters of history, philosophy and science astonished his elders, but his greatest talent lay in the art of war, the purpose for which his gene-father had created him. A genius for military organisation prompted his foster father to give him command of an expeditionary force in the far north of Macragge. This mountainous area was called Illyrium, a barbarous land which had harboured bandits and brigands for as long as anyone could remember. Although many wars had been fought against them, no-one had ever pacified the region for long. Roboute fought a brilliant campaign and won not only the submission, but also the respect, of the fierce Illyrian warriors. Returning home, Roboute found the capital of Macragge City in turmoil. During Roboute's absence his father's co-Consul, a man named Gallan, had crafted a coup d'etat against Konor. Gallan was one of many amongst the wealthy nobility of Macragge who were jealous of Konor's political power and popularity. These malcontents were accustomed to easy living on their vast estates where they were supported by the toiling of a multitude of impoverished slaves. Konor had changed all that, forcing the old aristocracy to provide their vassals with reasonable accommodation and sufficient amounts of food. He had also passed legislation which obliged them to contribute to an ambitious programme of improving and enlarging the capital city. All these reforms were of great benefit to the people of Macragge, but were unpopular with all but a few of the more far-sighted aristocrats.

As Roboute and his army approached Macragge City, they saw the smoke from a multitude of fires and hurried to investigate. From citizens fleeing from the city, Roboute learned that troops in the pay of Gallan had attacked the Senate House with Konor and his loyal bodyguard inside. The rebels surrounded the Senate, whilst drunken soldiers roamed the city looting and murdering at will. Roboute hurried to his foster father's rescue. Leaving his troops to      deal with the drunken mob, he fought his way into the Senate House. There he found his father dying of wounds inflicted by an assassin in Gallan's employ. For three whole days the Consul had directed the defence of the building, even as surgeons fought for his life. With his dying breath Konor told his son of Gallan's treachery.

Roboute crushed the aristocratic rebels and quickly restored order to the city. Thousands of citizens flocked to the Senate House and amidst a wave of popular acclaim Roboute assumed the mantle of sole and all-powerful Consul of Macragge. The new ruler acted swiftly to crush the old order. Gallan and his fellow conspirators were executed and their lands and family titles taken from them. New, honest, hard-working settlers were given their old farms and property. With super-human energy and the vision only a Primarch was capable of executing, the Consul reorganised the social order of Macragge, rewarding the hard-working, placing men of honour in high office, and building the armed forces into a powerful and well-equipped force. Macragge flourished as never before.

Arrival of the Emperor
While the gestation capsules containing the Primarchs drifted through the Warp, the Emperor and his armies of Space Marines advanced across the galaxy. This Great Crusade liberated many human worlds from alien domination and re-established contact with human-settled planets that had endured isolation and danger for untold thousands of years.

As the young Roboute Guilliman waged war against the Illyrian bandits in the northern mountains of Macragge, the Emperor and a force of Space Marines reached the planet of Espandor in a neighbouring star system. From the Espandorians, the Emperor learned of the existence of Macragge and the astounding son of Consul Konor Guilliman. He immediately realised that he had found one of his long-lost sons. Though the Emperor took ship to Macragge his vessel ran into a sudden and unexpected Warp-squall, a brief but intensely strong disturbance that threw the craft far off-course. By the time the Emperor reached Macragge, Roboute Guilliman had ruled for almost five standard years. In that time the world had undergone a transformation. Its people were well-fed and prosperous, its armies well-equipped and its cities had been rebuilt in glittering marble and shining steel. Vessels from Macragge plied regular trade with the local star systems, bringing raw materials and more people to the flourishing world. The Emperor was astounded to find a planet so well-ordered and prosperous, and realised at once that Roboute Guilliman was a Primarch of unsurpassed ability and vision. Once Guilliman learned the truth of his origins he immediately swore his fealty to the Emperor, his true father.

The XIII Legion of Space Marines, the Ultramarines, was assigned to the command of Roboute Guilliman, whose own genome had provided the basis for its Astartes' gene-seed, and its forward base was relocated to Macragge. The Primarch quickly assimilated the many wonders of the Imperium of Man and set about his new role with skill and enthusiasm. Guilliman's chief talents, as ever, lay in war, and he led the Ultramarines to fresh conquests in the galactic south. He succeeded in liberating more worlds during the Great Crusade than any other Primarch, and the worlds he brought within the Imperium were to benefit from his organisational skills and passion for efficient government. Whenever Roboute Guilliman freed a world from the tyranny of xenos or other men, his first priority was to set up a self-supporting defence system. Once a world was safe he could move on, leaving behind enough advisers to ensure that industry would be created, trade routes set up with the rest of the Imperium, and government directed towards the betterment of the people.

Great Crusade
Roboute Guilliman quickly assimilated the knowledge required for him to lead a Space Marine Legion, and took full command of his Astartes. His greatest talents had always lain in the art of war, and he led his soldiers to victory after victory, liberating countless worlds from oppression by alien races and human tyrants ignorant of the light of the Emperor of Mankind, fighting in a way that caused minimal collateral damage, and winning over the hearts and minds of the people. Back on Macragge, the Ultramarines who had remained behind began construction of the Fortress of Hera, the Legion's fortress-monastery, and oversaw the training and genetic modification of new recruits. The Ultramarines' efficiency and wide recruitment pool soon saw the Ultramarines Legion swell in size, becoming by far the largest of the twenty Space Marine Legions. While most of the Legions had over 10,000 members, at their height the Ultramarines possessed in excess of 250,000, putting them on a par with the Word Bearers Legion, who maintained approximately 100,000 Astartes. When the Emperor proclaimed Horus, the Primarch of the Luna Wolves Legion and his personal favourite as the Warmaster of the Imperium, Guilliman accepted the news without resentment, and Horus continued to seek his counsel. However, Horus believed that Guilliman felt that he had deserved the honour of being named Warmaster just as much, if not more.

Meanwhile, the fortress-monastery of the Ultramarines grew on Macragge. Some Ultramarines remained behind to supervise the work, which progressed rapidly thanks to the trading network and advanced industries of the planet. Within a        year a training base was established, and recruiting for the Legion began on the planet Macragge and the surrounding worlds. It was not long before the Ultramarines Legion received its first influx of warriors born and bred on Macragge rather than Terra. Thanks to the thoroughness of their organisation, the Ultramarines were able to receive constant recruits throughout the Great Crusade. Because of their strong recruitment base and Roboute Guilliman's tactical expertise, the Ultramarines soon became the largest of the Space Marine Legions, having more recruits and suffering fewer casualties than any other Legion.

Battle of Calth
When the Warmaster Horus turned his back on the Imperium, swore his allegiance to the Ruinous Powers of Chaos, and began the Horus Heresy, his first act before making his break with the Emperor of Mankind open was to lure away as many Loyalist Legions from Terra as possible. Horus ordered Guilliman to lead an expeditionary force to the world of Calth in the Veridian System in the Realm of Ultramar to prepare for a campaign in the Eastern Fringes of the galaxy, where, Horus claimed, an Ork WAAAGH! was massing. Horus expected the Ultramarines to await the arrival of the Word Bearers who would join with the XIII Legion in prosecuting a camapign against the Ork menace. Unknown to Guilliman, the XVII Legion had long before turned Traitor in service to the Chaos Gods, and its Primarch, Lorgar, gleefully accepted Horus' orders to close the trap on his Legion's long-hated rivals. The Word Bearers' sudden attack decimated Guilliman's Legion fleet, and the Ultramarines' ground troops quickly found themselves impossibly outnumbered by their former allies as the infamous Battle of Calth erupted. The Word Bearers slew their Loyalist foes in droves in the early stages of their surprise attack and pushed them back over huge stretches of territory. The Traitors rejoiced at the terrible blows they were inflicting upon the Legion that had once aided the Emperor in humiliating them upon the world of Khur decades before the start of the Heresy when they had been taken to task for repeated violations of the atheistic philosophy known as the Imperial Truth. Unknown to them, Guilliman's flagship, which had survived the initial Word Bearers' attack on the Ultramarines fleet, effected emergency repairs and regrouped with the other surviving Ultramarine starships in space. Having taken stock of his remaining forces, Guilliman sent an immediate astropathic distress call to Macragge. The Loyalist Marines on Calth, Ultramarines all, had been forced into a fighting retreat, but soon occupied fortified positions. Many Ultramarines had been born on Calth, and proved more resolute than the Word Bearers anticipated. In space, Guilliman's vessels began hit-and-run attacks on their over-confident enemy. Guilliman assessed his ground troops' positions and broadcast clear, concise orders to each pocket of defence, coordinating them into a cohesive force. One Ultramarine force led by Captain Ventanus led a breakout and retook Calth's Defence Laser silos, aiding the sorely-pressed Ultramarines fleet from the surface of Calth. Guilliman's depleted forces slowed the Word Bearers down long enough for the remainder of the Ultramarines Legion to arrive and rout the Traitor Marines from the system, though at a heavy cost. The Word Bearers turned Calth's own orbital defence platforms on the Veridian star, stripping away the outer layers of its photosphere and destabilising it, ultimately rendering the surface of Calth uninhabitable. At the same time, the Word Bearers had used the battle taking place on Calth to summon a massive Warp Storm called the Ruinstorm, that was intended to cut off Ultramar from the rest of the galaxy and prevent the Ultramarines from providing any reinforcements to Terra as Horus made his assault upon humanity's homeworld. The eruption of the Ruinstorm cut off Calth from the main body of the Ultramarines Legion and left the Astartes of the XIII Legion trapped on Calth locked in a brutal subterranean war with those Word Bearers units that had also been left behind when their Legion retreated from the Viridian System. Yet Roboute Guilliman and a large portion of his Legion had remained off-world as a result of the Word Bearers' devious assault upon the Ultramarines fleet. Bloodied but unbowed, the Ultramarines received the orders of Malcador the Sigillite, the Emperor's Regent, while he was indisposed pursuing the secret Imperial Webway Project, and prepared to meet the needs of the Imperium's defence against the Traitor Legions as best they could.

Shadow Crusade
In his wrath, the Lord of Ultramar had gathered what vessels he could spare after Kor Phaeron’s ambush, drawn additional numbers from the first Ultramarines relief fleet bound for Calth after the massacre above that world, and tracked Lorgar directly through the use of the XIII Legion’s own astropathic choirs. In the wake of the Battle of Calth, the Word Bearers Legion, led by Lorgar, linked up with Angron and his World Eaters Legion to launch a Shadow Crusade against the Realm of Ultramar's Five Hundred Worlds in an attempt to spread the massive Warp Storm known as the Ruinstorm that had been conjured by the Word Bearers' First Chaplain Erebus at Calth across the Eastern Fringe. This prodigious Warp Storm would effectively split the galaxy in half and deny needed reinforcements to the Loyalists as Horus drove on Terra in an attempt to overthrow the Emperor of Mankind.

The Shadow Crusade laid waste to 26 worlds until Guilliman's retribution fleet finally caught up to the Traitors upon Angron's homeworld of Nuceria, which the World Eaters Legion were preoccupied with wiping clean of all life in vengeance for the treatment the Nucerians had merited out a century before to Angron. The XIII Legion warship Courage Above All, Guilliman's temporary flagship, broke Warp at the system’s edge, at the head of a large void armada consisting of 41 vessels. The Ultramarines armada looked wounded, cobbled together from separate fleets. It was not a dedicated interdiction war-fleet, but clearly a ragtag strike force, a lance thrust to the enemy’s heart. Guilliman himself had done the best he could with limited resources. The XIII Legion's Cruisers and Battleships ran abeam of the enemy fleet for repeated exchange of broadsides, offering targets too big and powerful to ignore, while the rest of the Ultramarines fleet used calculated Lance strikes from safer range. The armada then divided its assault potential, doing its utmost to destroy Lorgar's flagship Fidelitas Lex, and attempted to take the World Eaters' flagship Conqueror in a boarding action.

But the Ultramarines' warships not only fought a void war, they also attempted to take the fight to the surface of Nuceria, for this attack was personal. The Ultramarines had come for revenge against Lorgar and the Word Bearers, just as they had pursued Kor Phaeron all the way to the Maelstrom on the other side of Ultramar. Several Ultramarines warships attempted to make a run on Nuceria, haemorrhaging Drop Pods, landers and gunships, forcing planetfall by any means necessary. The Ultramarines fleet swept over and against the Traitors like an insect horde. But the tenacious commander of the Conqueror, Lotara Sarrin, put up a difficult fight and destroyed a number of Ultramarines vessels that attempted to make a run for the surface. Though the World Eaters' flagship transformed a number of the smaller vessels into flaming wreckage, the Ultramarines eventually punched through her tenacious defence and managed to land troops on the surface of Nuceria.

Meanwhile, the Fidelitas Lex was already a ruin, its armour pitted and cracked, its shields a memory. The cathedrals and spinal fortresses barnacling along its back were gone, laid waste by the Ultramarines’ incendiary rage. The XIII Legion's armada attacked in strafing runs and protracted exchanges of broadsides, trading fire with the superior warship and accepting their own casualties as the cost of bleeding the bigger vessel dry. Each assault left the Lex weaker, firing fewer turrets and cannons, taking punishment on its increasingly fragile armour. But she  fought on. Crawling with smaller ships, the Lex lashed back with its remaining Macro-cannons, rolling in the light of its own burning hull. Guilliman guided the battle from the command deck of Courage Above All, and had decided that the Lex would die first, killed in the death of a thousand cuts and swept from the game board, while the Conqueror would be boarded and killed from within. In the course of the battle in Nucerian orbit, the Conqueror could not rise to its sister-ship’s defence. Both Traitor Legion flagships fought alone, starved of support and suffering the endless attacks of the XIII Legion’s ragged armada. Salvation Pods streamed from the Lex’s sides and underbelly, along with heavier Mechanicum craft and bulk landers. With the Legionaries of the Word Bearers already on the surface, the ship’s human population fled in the vessel’s final minutes. And still the great vessel fought -- rolling, turning, raging. The Ultramarines Cruisers that drifted past burned as badly as the warship they were killing. This void battle was a form of dirty fighting between warships, too close for the neat calculations of ranged battery fire. Instead, it was an up close and personal slugfest.

The Ultramarines Battle Barge Armsman intercepted the Conqueror and came abeam, launching Assault Carriers and Boarding Torpedoes. While the World Eaters flagship was busy repelling boarders, a number of smaller XIII Legion vessels slipped past her defences and launched Drop Pods, gunships and troop carriers. The first Drop Pods hammered home on the planet's surface. Sealed doors unlocked and the first Ultramarines poured forth, Bolters raised, moving in perfect and well-trained unity. But the World Eaters were waiting for them. Those not lost to the Butcher's Nails at once had the presence of mind to note that these Ultramarines were not the pristine cobalt-blue warriors they had previously faced on the War World of Armatura. These Legionaries of the XIII wore cracked Power Armour, still scarred and burnwashed from some horrendous battle weeks or months before. These were hardened veterans of the Calth Atrocity. They burned with a cold intensity to carry out the vengeance in their hearts, and were intent on getting to grips with the Word Bearers.

As was their way, the Ultramarines established footholds at defensible positions, clearing room for their reinforcements to land. For every position they held, another was overrun by the World Eaters in a storm of roaring axes, or lost to the Word Bearers' chanting, implacable advance. The XII Legion crashed against the XIII in rabid packs, showing why Imperial forces had feared to fight alongside them for decades. Uncontrolled, unbound, unrestrained, they butchered their way through Ultramarines strongpoints, enslaved to the joy of battle because of the Butcher's Nails cortical implants sandwiched within the meat of their minds. The XVII Legion also met their Loyalist cousins, replacing ferocity with spite and hate. The Ultramarines returned it in kind, hungry for vengeance against the vile Traitors who had defiled Calth and damaged its star. Word Bearers units marched, droning black hymns and chanting sermons from the Book of Lorgar, bearing corpse-strewn icons of befouled metal and bleached bones above their regiments.

As the fighting raged, the burning shell of the Fidelitas Lex cut through the clouds into the planet's atmosphere, shuddering on its way east, rolling ever downwards, achingly slow for something of such scale. The weight of the Lex's massive plasma engines dragged the stern down first, colliding with the Nucerian ocean's surface far from shore. In the meantime, the demigod in gold and blue had finally found the object of his obsession amidst the clamour of war. Guilliman confronted Lorgar, possessing the advantage of two weapons, but Lorgar's Crozius gave him a reach his brother lacked. When they first met, there was no furious trading of frantic blows, nor were there any melodramatic speeches of vengeance avowed. The two Primarchs came together once, Power Fist against War Maul, and backed away from the resulting flare of repelling energy fields. Their warriors killed each other around them both, and neither Primarch spared their sons a glance. Lorgar flicked the clinging lightning from the head of his Crozius, shaking his head in slow denial.

Both Primarchs fought without heeding their warriors, their godlike movements an inconceivable blur to the Space Marines fighting around them. None had ever imagined the heroes of this new age would take the field against each other, nor could they have predicted the wellsprings of spite between them. Guilliman confronted Lorgar for what his Legion had done across the Five Hundred Worlds of Ultramar. In his righteous anger the Ultramarines Primarch struck Lorgar with one of his fists, battering the Word Bearers Primarch's sternum. Lorgar repulsed him with a projected burst of telekinesis, weak and wavering, but enough to send his brother staggering. The Crozius followed, its power field trailing lightning as Lorgar hammered it into the side of Guilliman’s head with the force of a cannonball. Both Primarchs faced each other beneath the grey sky, one bleeding internally, the other with half of his face lost to blood sheeting from a fractured skull.

As the two Primarchs were locked in their furious life-and-death struggle, they were oblivious to the destruction being wrought around them. Suddenly, Angron burst forth from the Ultramarines ranks, his armour a shattered wreck, and both of his Chainswords spat gobbets of ceramite armour plating and scarlet gore. Angron was plastered with the blood of the slain after hours in the crush of the front lines of intense combat. On his chest hung a bandolier of skulls taken from the mass grave at Desh’elika Ridge. Blood painted them as surely as it marked Angron. Even through the constant pain generated by the Butcher's Nails, that pleased him. He wanted his deceased brothers and sisters to taste blood once more. He had carried them with him across Nuceria, letting their empty eyes witness the razing of his former, hated homeworld. The World Eater launched himself at Guilliman with murderous hatred. The two Primarchs fell into a seamless, roaring duel where Lorgar and Guilliman had abandoned theirs. Guilliman was forced back by the storm of Angron's blows.

As the two Primarchs fought, Guilliman landed a glancing blow, his fist pounding across Angron's breastplate. One of the skulls of Angron's fallen kinsman that hung from the chain worn across his breastplate was partially shattered and scattered across the ground. Guilliman stepped back, his boot crushing a skull's remnants to powder. Angron saw it, and threw himself at his brother, his howl of wrath defying mortal origins, impossibly ripe in its anguish. Lorgar saw it, too. The moment Guilliman's boot broke the skull, he felt the Warp boil behind the veil. The Bearer of the Word started chanting in a language never before spoken by any living being, his words in faultless harmony with Angron's cry of torment. Lorgar enacted his dark plan to save his brother's life, summoning the Ruinstorm to the world of Nuceria, tearing the sky open and unleashing a crimson torrent, formed from the ghosts of a hundred murdered worlds, raining blood. Guilliman had been holding his own against both Traitor Primarchs, until Lorgar ceased his attack and started his achingly resonant chant. Angron and Roboute still fought, with the Lord of the Ultramarines giving ground each time Angron landed a blow. Angron plunged his Chainsword up under Guilliman’s breastplate -- a shallow stab, but a telling one. The Ultramarines Primarch crushed the impaling sword in one fist and staggered back, truly bleeding now.

Despite the maelstrom of combat and sorcery raging around them, Angron still fought Guilliman, standing above the kneeling Ultramarine Primarch. He had not even noticed the storm of blood streaming from the sky in a red torrent. Sparks sprayed from Roboute’s raised gauntlets as he struggled to ward off blow after blow. He was beaten and down. His wounds bled profusely, a palette of proud defeat. His warriors fought desperately to retrieve him. Fortunately they were granted a brief reprieve, as Lorgar's incantation locked up Angron's muscles, and began to transform the Red Angel into a new form as a Daemon Prince of Khorne. Guilliman took the opportunity to escape into his sons' defiant phalanxes, retreating in enviable unity. Lorgar saw the expression of disgusted awe on his brother's face as the wounded Ultramarine stared at Angron's metamorphosis atop the mound of dead sons from all three bloodlines of Space Marines. The XIII Legion continued to fire even in retreat, leaving the world of Nuceria battered and bloody. Their campaign against the two Traitor Legions was over..for now.

Roboute Guilliman escaped from Nuceria, unable to face or even fully comprehend what both of his brothers had become through their corruption by the Ruinous Powers. The World Eaters completed their purge of Nuceria until not one human life remained on the benighted world. Angron, now the very embodiment of the Blood God's Eight-Fold Path, shook the dust of the world from his feet and did not think of it again.

Battle of Terra
As the long and bloody years of the Horus Heresy passed, the Traitor Legions under the command of the Warmaster Horus finally closed on the homeworld of Mankind and launched their great assault against the Imperial Palace while they believed a good portion of the Loyalist Space Marine Legions remained occupied in other regions of the galaxy. While the Forces of Chaos came close to battering down the gates of the Palace, the Loyalists' stout defence managed to hold the line long enough for Loyalist reinforcements to drop from the Warp on the edges of the Sol System. Salvation was coming. In orbit of Terra, Horus' allies delivered the fateful news to the Warmaster while he sat directing the battle for the Imperial Palace. The Ultramarines, Dark Angels and Space Wolves Legions were only hours away from reinforcing the Emperor and his Loyalist defenders. Horus knew that his gamble had failed. What happened next is disputed, some believe Horus disabled his shields as he experienced one last moment of regret, and some believe it was a personal challenge to the Emperor. Nevertheless, Horus lowered the shields of his flagship Battle Barge Vengeful Spirit, allowing the Emperor, the Blood Angels' Primarch Sanguinius and a company of Imperial Fists to teleport aboard and slay him, ending the Horus Heresy. The Emperor was mortally wounded in the exchange and interred in the Golden Throne immediately afterwards by the Primarch Rogal Dorn, leaving a dangerous void of power and authority in the Imperium.

The Ultramarines did not arrive until after Horus' defeat, and they found Terra and the Imperium in ruins. Guilliman steadfastly refused to allow the Imperium to fall, and began dispatching elements of his Legion to all corners of the galaxy to stem the tide of invasion and unrest as the other Loyalist forces recovered and rearmed. After a decade of intense fighting, stability was restored. To prevent a single commander having as many superhuman Astartes at his command as Horus had, Guilliman reformulated the sizes of all of the Loyalist Space Marine Legions into thousand-man Chapters, breaking apart the 9 original Loyalist First Founding Legions into the much smaller Second Founding Chapters. Never again would one man, no matter how noble and unblemished his motives, wield the power of an entire Space Marine Legion. The rationale and proper organisation of Space Marine Chapters are the main topic in Guilliman's masterwork of strategy, the Codex Astartes.

Whilst the Horus Heresy plunged the Imperium into savagery and civil war, the Ultramarines were engaged on the southern edge of the galaxy. Their very success had carried them far from Terra and isolated them from the conquering Traitor Legions of Warmaster Horus which had been concentrated in the galactic northeast. News of Horus' treachery did not reach the Ultramarines until the attack on Earth was underway. Thanks to the speed of Horus' attack there was little that Roboute Guilliman could do in support of his Emperor during the crucial Battle of Terra. None of the worlds already liberated by the Ultramarines were in serious danger from the Forces of Chaos. Consequently, the Ultramarines were poorly placed to contribute during the early stages of the Horus Heresy.

Post-Heresy Imperial Reformation
As fate would have it, the Ultramarines were therefore largely untouched by the fighting of the Horus Heresy. Other Loyalist Space Marine Legions had lost thousands of troops during the fighting, and half of the original 18 Legions had sided with Horus and been corrupted by Chaos. As a result, the number of Astartes left to the Imperium was very few, yet never were they more needed.

The confusion and disorder following the Horus Heresy had left the Imperium weak and vulnerable. Everywhere the enemies of mankind prepared to attack. Many worlds remained in the grip of Chaos. Into this breach stepped Roboute Guilliman and the Ultramarines. Always the largest of the Astartes Legions, the Ultramarines found themselves divided and dispatched all over the Imperium in a desperate effort to stem the tide of invasion and unrest. The Ultramarines successfully held the Imperium together during a time of intense danger. Macragge was able to supply new recruits at such a rate that before long the Ultramarines alone accounted for more than half the total number of Space Marines, and few were the star systems where their heroism went unnoticed. Within a decade, order was restored to the Imperium. Even as the Ultramarines reconquered, a new theory of warfare was emerging. Under the guidance of the Ultramarines' Primarch, the Codex Astartes was taking shape. Its doctrines would reshape the future of all Space Marines and forevermore dictate the foundation for the Imperium's military strength and the ultimate survival of Mankind.

The Second Founding of the Space Marines was decreed seven years after the death of Horus and the end of his Heresy. Most of the old Loyalist Legions divided into fewer than 5 Successor Chapters, but the Ultramarines were divided many times. The exact number of Successor Chapters created from the Ultramarines is uncertain: the number listed in the oldest copy of the Codex Astartes gives the total as 23, but does not name them. With the Second Founding, the size of the Ultramarines force was much reduced. Most of the Space Marines left Macragge to establish new Chapters elsewhere. The Ultramarines' fortress-monastery was built to accommodate more than ten times as many Space Marines as now remained on their homeworld. As a result its arsenals and weapon shops were partially dismantled and taken by the new Chapters to found their own bases. The genetic banks of the Ultramarines, and the huge recruitment organisation, were similarly reduced. As a result of the Second Founding, the Ultramarines' gene-seed became pre-eminent across the Imperium. The new Chapters created from the Ultramarines during the Second Founding are often referred to as the Primogenitors, or "first-born". The lasting heritage of Guilliman was not only genetic, but spiritual. Even to this day, 10,000 standard years later, all the Primogenitor Chapters venerate Roboute Guilliman as their own founding father and patron, and hold the ruler of Ultramar, whoever he be, as the exemplar of all that it means to be a Space Marine. So did the Ultramarines rise to become preeminent amongst their brother Chapters.

Roboute Guilliman continued to serve with the Ultramarines Chapter, leading them for a hundred years after the Second Founding. It was said that during those years, Guilliman led several incursions alongside his brother Primarchs against the remaining Chaos Space Marines. During one incursion, Guilliman faced his former brother Primarch Alpharius of the Alpha Legion, and slew him in single combat (though the precise details of this event remain in doubt, even to the Ultramarines). The Ultramarines, however, were forced to withdraw from the combat, as to their shock the Alpha Legion's Traitor Marines fought on despite the apparent loss of their Primarch. Guilliman would meet eventually his ultimate fate a century after the Second Founding, during the Battle of Thessala in 121.M31, when he encountered one of the Traitor Primarchs, Fulgrim of the Emperor's Children, who had become a Daemon Prince of Slaanesh. During this encounter with his former brother, Fulgrim managed to fatally injure Guilliman in the neck with a poisonous sword (which was remarkably similar to the Anathame sword that was used by Dark Apostle Erebus to fatally wound Horus on Davin's moon). Fatally poisoned by his one-time brother, Roboute was transported back to Macragge in a stasis field, and has remained entombed in the field for 10,000 years, frozen in time. Although physically impossible within the null-time of a stasis field, it is believed by many pilgrims to his shrine that his wounds are healing, and that one day he will awaken again when the Imperium needs him most. The Shrine of Guilliman built to contain his body is one of the most holy places in the entire Imperium, and one which welcomes millions of pilgrims every year. It lies within the Temple of Correction, a vaulted sepulchre forming a small part of the Ultramarines' vast northern polar fortress on Macragge. The temple is a miracle of construction and typical of the attention to detail to which the Ultramarines apply themselves. Its proportions defy the human mind by the scope and grandeur of its design. The multi-coloured glass dome that forms the roof is the largest of its kind. Even the Techno-magi of the Adeptus Mechanicus come to marvel at the structure said to have been designed by Roboute Guilliman himself. According to the Ultramarines there is enough marble within the temple to build a mountain, and sufficient adamantium and shining plasteel to construct a sizable Imperial warfleet.

Within this edifice is the great marble throne of Roboute Guilliman, and upon that throne sits a regal corpse. Though the best part of 10,000 years have passed since his death, the Primarch's body is perfectly preserved. Even his death wounds from Fulgrim's blade are visible upon his throat. His mortal remains are preserved from the ravages of time by means of a stasis field that isolates the Primarch from the time-stream of normal four-dimensional space-time. Everything encompassed by the field is trapped in time and can neither change nor decay. There are some, however, who claim the Primarch's wounds do change. They say that Guilliman's body is slowly recovering and that his wounds show mysterious signs of healing. Others deny the phenomena, and point out the sheer scientific impossibility of change within the stasis field. Yet enough believe the stories to come and witness for themselves the miracle of the Primarch, generation after generation.