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Imperial Thunder Warrior captain during the Unification Wars.

The Thunder Warriors, also sometimes referred to in ancient records as the Thunder Legion and the Thunder Regiments, and known in High Gothic as the Legio Cataegis, were the 20 regiments or legions of genetically-engineered, superhuman warriors of Terra created by the design of the Emperor of Mankind through alchemical augmentation, somatic gene-sculpting and muscle-grafting techniques.

Their purpose was to unite the homeworld of Humanity beneath the Emperor's rule during the Unification Wars on Terra in the late 29th and 30th Millenniums.

They were the first gene-enhanced warriors created by the Emperor and served as the precursors to the present-day Space Marines, though they were created from adult male supporters of the Emperor rather than adolescents.

The Thunder Warriors' legions were commanded by genetically-identical Cataegis warriors of particular skill, intellect and mental stability, who each held the rank of "primarch." Each legion was particularly focused on a particular tactical or strategic specialty similar to the later, more perfected pattern seen among the Legiones Astartes.

Wrought to be living weapons, the Thunder Warriors were known to be physically stronger, more savage, more resilient and more potent in combat than the later Astartes, though they were not as long-lived and suffered from often dangerous mental instability and early metabolic collapse when their bodies began to reject their augmentations.

Imperial chronicles hold that the last of the legendary Thunder Warriors died heroically during the final battle of the Unification Wars in the later years of the 30th Millennium that reunified Terra beneath the single rule of the Emperor and forged the government that would become the Imperium of Man.

The truth of the matter was far different, for the Thunder Warriors' fate was bound up in the terrible price that the Emperor proved willing to pay to secure a better future for Mankind.


Imperial Thunder Warrior standard bearer during the Unification Wars.

Age of Strife

During the turbulent era known as the Age of Strife or "Old Night" on Terra, the Sol System and the other nearby star systems that had been colonised by Humanity during the Age of Technology were effectively cut off from interstellar travel or Astropathic communication with each other.

This was due to the massive Warp Storms that swept the galaxy as the Immaterium was roiled by the millennia-long gestation of the Chaos God Slaanesh and the turbulence that marked the decay of the Aeldari Empire before The Fall.

During the five millennia of anarchy, fear and violence that marked this period, Old Earth's once unified planetary government had completely broken down and been divided into dozens of warring techno-barbarian nations. Continuous warfare raged across the surface of Terra for two and a half thousand years, beginning in the late 27th Millennium.

Little remained of the once sophisticated civilisation of Old Earth's glorious past as techno-barbarian warlords and their gene-enhanced warrior-hordes continuously fought over the planet, which became little more than a massive battleground for their apocalyptic wars of attrition over the course of the millennia.

It was during this dark time that the Emperor of Mankind developed the first genetically-engineered warriors to serve in His armies. These were the proto-Astartes, who were created like the later generations of true Space Marines from advanced genetic engineering techniques, though these were not as efficient as what was used later to create the Space Marines. Nor was the technology involved as advanced or the geneticists as entirely willing, for some were captives the Emperor had taken during the Unification Wars.

The Emperor wrought these proto-Astartes to be faster, stronger and more powerful than any of the feral barbarian gene-sept warriors that claimed fealty over the various techno-barbarian nation-states of Old Earth. These warriors were a gestalt mix of unprecedented superhuman physical power, gene-programmed resistance to environmental and even psychic attack, a warlike spirit and the Emperor's own strategic genius.

The twenty Thunder Regiments were an army unlike any that had come before them, and the forces of the powerful tyrants of Old Earth had nothing to match them. These genetically-enhanced soldiers were created to drag their world back from the anarchy into which it had fallen.

It was against this backdrop that the mysterious saviour who would become known only as the Emperor revealed Himself -- the raptor's head and lightning banner marching proudly before the unstoppable armies of His Thunder Warriors.

Unification Wars

The Raptor Imperialis, early iconography of the Imperium of Man, utilised by the Thunder Warriors during the Unification Wars.

Emerging from anonymous obscurity in the late 29th Millennium, the Emperor took a direct and public hand in the future of Humanity for the first time in its history, conquering the various warring factions of Mankind's homeworld and establishing his direct rule over Terra during the Unification Wars.

The Emperor accepted the deaths of the many innocents that resulted from this conquest with great remorse in order to achieve the greater good of unifying Humanity and protecting it from the manifest predations of the Warp and the more vicious xenos of the galaxy. Unimaginably large, full-scale battles during the Unification campaign would last for weeks on end, with body counts in the millions that sundered mountains and split entire continents.

Future Imperial scholars would later dismiss these victories as lurid hyperbole, refusing to believe that such clashes of arms could possibly have been fought, but indeed they were.

The Imperial historical chronicles tell of the last battle of the Unification Wars, known as the Battle of Mount Ararat, which was fought in the Kingdom of Urartu. During this final battle the remaining Thunder Warriors were slain to a man.

The chronicles recorded that the famed Thunder Warrior Arik Taranis, known as the "Lightning Bearer," raised the Banner of Lightning at the final declaration of Unity which established the rule of the Emperor of Mankind over the entirety of Terra before dying of his wounds. It was a measure of the Thunder Warriors' heroic sacrifice that they had all died to win the last and greatest victory for the Emperor.

Unfortunately, this heroic version of events was completely false. The Thunder Warriors had not died to a man during the final battle of the Unification Wars. They had been brutally culled from existence by the Emperor's own servants on His orders. The Thunder Warriors had been destroyed by their own creator, a secret skillfully concealed from the people of the Imperium for more than 10,000 Terran years.

The Culling

An example of the prototype Mark I Thunder Power Armour used during the Unification Wars.

To carry out His plans for Humanity, the Emperor accepted that He would have to take certain actions that were essentially immoral in order to achieve the greater good of Mankind.

In the years to come, the Emperor needed the people of Terra to unite behind a single, dominant leader in order to begin the future re-conquest of the galaxy during the Great Crusade He intended to unleash next.

To create His legend, and unite all of Mankind behind His rule as an enlightened and invincible leader, the official record had to reflect that the Emperor had largely won the war and reunified Terra single-handedly.

Additionally, the Thunder Warriors were not like the Astartes who would follow them; they had been created solely for war and were not well-suited to any other activities. Once peace came to Terra, the Thunder Warriors would inevitably pose a risk to the new state's stability through their very existence and the flaws that had resulted in much mental instability and early deaths due to metabolic collapse among their ranks.

The Thunder Warriors had been enhanced as mature, adult men and their bodies often rebelled against the genetic changes only a few short Terran decades after the transformation. All this meant that the Thunder Warriors could not be allowed to survive the conflict they had been created to fight.

At first the Emperor simply did not replace their numbers as they fell to battle or insanity, but then decided to take more active measures. According to Arik Taranis, the final culling of the Thunder Warriors took place following the victory of the last battle of Unity, and was carried out by the Legio Custodes, the only soldiers in the Imperial armies capable of defeating the Thunder Legions.

In truth, the Emperor had been right to be worried about His creations. Another source claims that even before the Unification Wars had ended, the Thunder Warriors at last realised that their creator had cursed them with short lifespans as a result of their imperfect genetic augmentations, and turned upon Him for what they saw as His betrayal.

It was a cadre of several hundred Custodians, even then believed to have been led by the legendary Constantin Valdor, and accompanied by several thousand prototype Astartes of the I Legion of the newborn Space Marines, that stood in the Emperor's defence, carrying out a merciless culling of the obsolete and rebellious gene-soldiers.

Though some Thunder Warriors successfully escaped the cull, however it happened, the vast majority of those who survived the Unification Wars died at the hands of their own allies.

Individually or in small groups -- like the self-stylised "Dait'Tar" Thunder Warriors present during the Cerberus Insurrection of the early Great Crusade period -- some Thunder Warriors would survive, living mostly anonymous and miserable lives amongst the population of Terra, all honours of the past forsaken, always fearful of being discovered.

Fortunately for these survivors, the Imperium, believing them all dead, never truly sought to hunt them down, as all efforts were by then concentrated on the progress of the Great Crusade.


"Alas, for them, the warriors of caged thunder and with whom lightning smote, they have burned the brightest in glory, but burned brief."

Remembrancer Dolvar

An example of the Mark I Thunder Power Armour used by the Imperial Thunder Warriors at the time of the Unification Wars.

Despite their many early victories in the Unification Wars, the Thunder Warriors were far from perfect. Some were mentally unstable, others suffered catastrophic biological failure unpredictably after a span of years, their own superhuman physiques turning against them in the end.

It seems obvious in retrospect that the Emperor knew early on that the nascent Imperium needed a more permanent and stable force of gene-enhanced warriors, so even while the Thunder Warriors waged war in the Emperor's name, He gathered about Him a team of savants and gene-wrights, some willing and others as captives taken from his foes, and constructed new genetics laboratories deep in the vast dungeons of his Terran fortress in the Himalazian (Himalayan) Mountains. This team became known as the Imperial Biotechnical Division.

The labour there went on for solar decades in absolute secrecy and resulted in the creation of the Primarchs and many other wonders of the Emperor's arcane and unmatched gene-craft, known and unknown. Yet the foremost of these creations were the twenty Space Marine Legions, the Legiones Astartes of legend.

Into their creation went all the secret history and genetic lore of the Age of Strife, hard wisdom gained through the success and failure of the Thunder Warriors who were the Space Marines' prototypes and the fruits of the Emperor's own inimitable genius.

The first among the Space Marines were hand-picked men from the Emperor's personal, mortal bodyguard. These volunteers were subjected to surgical, genetic and psychological modification. With rigorous training and appropriate mental conditioning they became not only immensely strong and tough, but iron-willed and disciplined, an unstoppable force whose loyalty to the Emperor was unflinching.

Quickly the process was refined and systematised, and the numbers of the new genetically-enhanced warriors, at first armed and armoured as the Thunder Warriors had been, grew swiftly. They were organised into twenty distinct regiments numbering at first no more than a few hundred warriors each, much like the superhuman soldiers they were to replace.

Although it remained a dire secret at the time, it is now widely believed that this division was more than a merely administrative one, as each regiment contained variant "gene-seed" encoding drawn from a different primogenitor Primarch.

This often manifested its influence in subtle and unexpected ways, not least of all in influencing and altering the psychological character of the genetically enhanced warrior. With the Astartes regiments expanding rapidly into legions with the intake of new blood from the areas of Terra that had already joined cause with the Emperor, the new warriors quickly eclipsed and replaced the mighty but far less disciplined and unstable Thunder Warriors. With the Space Marines at the forefront of Imperial efforts, victory followed victory in quick succession.

Though the Thunder Warriors were superior in every physical aspect of their creation to the later Space Marines, they suffered from one flaw the later Astartes would not -- their lifespans were extremely short. The Thunder Warriors were not created to live beyond the achievement of Unity.

This was a genetic flaw that may have been deliberately written into their DNA during their creation to assure that when their usefulness was at an end, these warriors would cease to exist so that they might be replaced by the more balanced transhuman warriors of the Legiones Astartes. The Thunder Warriors were created to be a broadsword rather than a scalpel like the Astartes who would come after them.

Unlike most Space Marines, the Thunder Warriors were cold-blooded, ruthless killers who possessed talents for nothing other than war. In many ways they represented the worst aspects of Mankind's nature rather than its best. As the Unification Wars drew to a close, the Emperor knew that He would still need the superior skills of gene-modified warriors in order to carry on His "Great Crusade" and conquer the galaxy.

It was for this reason that He had moved to craft the genetically-engineered warriors who were truly superior in every way to average Humans -- morally, spiritually and intellectually as well as physically. These perfections of the transhuman warrior template would become the first true Space Marines of the Legiones Astartes. The Thunder Warriors were discarded as imperfect tools that had served their purpose.

The present-day members of the Adeptus Astartes are not the ancient Thunder Warriors' equals in the realm of pure combat. Yet, though the Thunder Warriors were stronger, hardier and more resilient than the later Astartes, their genetic legacy was never meant to last beyond the achievement of Terra's Unity.

The proto-Astartes were a means to an end, the conquest of a single world, whilst their genetic successors were intended to travel to the stars and conquer a galaxy. The Space Marines were also to serve as living embodiments of all that Humanity could hope to achieve.

It is the great tragedy of the Imperium that while the Space Marines were created to represent the pinnacle of Human development, they ultimately proved as susceptible to the basic flaws of Mankind as any other mortal.


An early Space Marine of the Ultramarines Legion wearing Mark I Thunder Pattern Power Armour like that used by the Thunder Warriors.

Mark I Thunder Power Armour

The first pattern of power armour created for the Thunder Warriors and the first true Space Marines was the Mark I Thunder Pattern Power Armour, though the name was later assigned by the ancient Mechanicum after the fact and at the time of its use the suit was simply called "power armour."

It was developed from the powered combat armour worn by the techno-barbarians that plagued Terra near the end of the Age of Strife. It was used during the Emperor's campaign to retake and reunite the Terran solar system before the Great Crusade.

It was by no means unique to the first Space Marines -- in fact, the techno-barbarian warriors the Emperor fought during the conquest of Terra wore it too, and the Emperor's early forces of genetically-enhanced Thunder Warriors were wearing it even before the first true Space Marines were created.

However, because it was designed with fighting in a terrestrial environment in mind, it was not fully enclosed, with no means to support the wearer in a vacuum.

Only the upper body was powered, due in part to the fact that during the Emperor's conquest of Terra, ranged weapons were difficult to make due to technological constraints, and so a warrior's upper-body strength was his most important asset.

It takes its name from the thunder bolt and lightning symbol the Emperor used during the Unification Wars on Terra before He adopted the double-headed eagle known as the Imperial Aquila during the Great Crusade.

That emblem gave the suit its most common present-day name -- Thunder Armour. This early armour was produced on a completely local basis. There was no standard design, individual suits varied heavily and their exact designs were often a matter of personal taste.

The main part of the armour was the massive powered torso which enclosed the chest and arms. Coiled energy cables beneath the armour plating transmitted energy from the power pack on the back to the arms, greatly increasing the warrior's physical strength.

The legs of this mark of armour were not powered at all, but enclosed in tough padded breaches, though simple steel plates were sometimes also used. Although uncommon, the best-equipped warriors sometimes wore armoured greaves and armoured boots.

However, this ancient suit of power armour was noticeably noisier than later models, perhaps due to the unpowered legs, making stealth operations nearly impossible in it.

Ranged Weapons

The Thunder Warriors were armed with an archaic, but large and powerful pattern of the standard Astartes bolter.

Notable Thunder Warriors

  • Arik Taranis, the "Lightning Bearer" - Arik Taranis was a Thunder Warrior whose name was famous throughout the Imperium and could awe even a modern Astartes with its historic resonance. There is not a Space Marine amongst the entirety of the Adeptus Astartes that does not know the name of Arik Taranis; the historic battles he helped to win, the foes he slew and the great honours he earned fighting in the Emperor's legions during the Unification Wars. Arik Taranis was history wrought into living form: the Victor of Gaduaré, the Last Rider, the Butcher of Scandia, the Throne-slayer -- these and a hundred other battle-honours earned by this warrior were scattered throughout the histories written about the foundation of the Imperium. All these tales culminated in the end of Taranis' life atop a once-flooded mountain during the final battle of the Unification Wars. Taranis was given the title "Lightning Bearer" in the aftermath of the Battle of Mount Ararat in the Kingdom of Urartu. The Imperial chronicles record that he died, succumbing to the damage caused by his wounds once he fulfilled the singular honour of raising the Emperor's Banner of Lightning at the final declaration of planetary Unity for Terra. Taranis and his Battle-Brothers had all been slain in this final battle of the great conflict, dying to win the last and greatest victory for the Emperor and establish his new Imperium of Man. The truth, however, was very different, for Arik Taranis survived the Battle of Mount Ararat, and also knew that the Emperor had founded his Imperium by betraying the men who had fought so ferociously for him. Amazingly, Taranis bore no ill-will towards his creator for his monstrous betrayal, for he understood better than anyone that the Thunder Warriors were merely a means to an end. He and all his kind had been cast aside by the Emperor in favour of the Legiones Astartes gene-template for the good of Humanity. Arik Taranis was one of only a very small number of Thunder Warriors who managed to escape the cull. Yet Taranis had learned what he could from his creator in the years of the Unification Wars, and came to master much of the ancient science of genetics that the Emperor had used to create the Thunder Warriors. Unfortunately, Taranis did not possess enough knowledge to halt his own deterioration, but just enough to desperately cling to life as a crime lord in Terra's Petitioner's City long enough to one day play a final role in the history of the Imperium during the Horus Heresy.
  • Ghota - Ghota was a Thunder Warrior who served during the Unification Wars and also somehow managed to survive the Cull alongside his former commander, Arik Taranis. Ghota continued to faithfully serve as Arik Taranis' lieutenant after he had taken over the Petitioner's City on Terra and become the feared crimelord known as Babu Dhakal. Ghota enforced the will of his master and the Dhakal Clan crime syndicate upon the Petitioner's City. Despite coming across as being somewhat of a simpleton and unintelligent, Ghota was fully aware of his and his brother's failing physical condition and understood what was needed of him to achieve prolonged life like his genetic successors, the Astartes. Ghota normally carried a huge Thunder Hammer into battle, and was more than a match for most Space Marines in one-on-one combat.
  • Skand - Skand was the first Thunder Warrior to fall in battle during the Unification Wars. His name was etched into the shrine of The Comet.
  • Dahren Heruk - Heruk was one of the few Thunder Warriors to survive into the era of the Horus Heresy. He was a veteran of the Unification Wars campaigns for Arat, Hy Brasil, Urhs, and Albia. Heruk had banded together with several other survivors of the Thunder Legion to fight in illegal gladiatorial combats in the Outer Palace region of the Imperial Palace complex on Terra. Heruk intervened during the Solar War when Alpha Legion Heretic Astartes infiltrators and their allied Chaos Cultists were attempting to carry out acts of subversion to prepare the throneworld for the coming invasion of Horus and the Siege of Terra. Heruk discovered a Possessed Alpha Legionary leading a group of eight cultists in a sacrificial ritual in the catacombs beneath the Outer Palace. Heruk aided one of the Legio Custodes in killing the group, though he was mortally wounded in the combat and asked the Custodian, Tagiomalchian, an Ephroi, to grant him an "Honoured Death," which he received. Heruk suffered, like many of the surviving Thunder Warriors of this period, from constantly reliving his past moments of military glory during the Unification Wars. These visions began to occur at all times, interfering with the Thunder Warriors' ability to differentiate reality from memory.
  • Kabe - Kabe was one of the few Thunder Warriors to survive into the era of the Horus Heresy. He had banded together with several other survivors of the Thunder Legion to fight in illegal gladiatorial combats in the Outer Palace region of the Imperial Palace complex on Terra. Kabe had fought in many of the battles of the Unification Wars, including against the Kievan Rus at the Sibir ice plain at Urhs, against the Hoth Grendal clans at Albia, and at the siege of Abyssna. However, he proved unable to defeat a chrono-gladiator and was mortally wounded. His opponent was slain by another Thunder Warrior, Dahren Heruk, who jumped down into the gladiatorial pit and gave Kabe an "Honoured Death" by stabbing him in the heart.
  • Gairok - Gairok was one of the few Thunder Warriors to survive into the era of the Horus Heresy. He had banded together with several other survivors of the Thunder Legion to fight in illegal gladiatorial combats in the Outer Palace region of the Imperial Palace complex on Terra. Gairok eventually succumbed to the madness claiming all the Thunder Warriors in which he was unable to distinguish between the present and the memories of his past in battle. He was killed in a bar in a run-down portion of the Outer Palace known as "the Swathe" by Dahren Heruk after he became lost in one of his memories and began to slay all of the other patrons, and could not be roused back to the present.
  • Vezulah Vult - Vult was one of the few Thunder Warriors to survive into the era of the Horus Heresy. He had banded together with several other survivors of the Thunder Legion to fight in illegal gladiatorial combats in the Outer Palace region of the Imperial Palace complex on Terra. Gairok had fought at the battle at Abyssna during the Unification Wars, where he had ordered his unit of Thunder Warriors to charge into the fray and take the northern tower of the enemy's fortifications alongside the Legio Custodes. Vult was attacked in the catacombs beneath the Swathe in the Outer Palace district by a Possessed Alpha Legion infiltrator and his cell of Chaos Cultists. He was tracked down by his partner and former comrade in the Thunder Legion Dahren Heruk who thought that he had also succumbed to the madness of the aging Thunder Warriors when he attacked and mortally wounded Tarrigata, the blind old man who had owned the Thunder Warriors gladiatorial lutus. When Heruk found him, Vult was already dying and made clear in his final moments that he had not fallen prey to the madness after all -- the real culprits were the servants of Chaos.
  • Ushotan - Ushotan was the primarch or commander of the 4th Legion of Thunder Warriors, who were known as the "Iron Lords." He had been chosen for the position due to his superlative command skills and was genetically no different from his warriors. Ushotan was considered a superlative warrior and general, gaining the respect of even the likes of Captain-General Constantin Valdor of the Legio Custodes. He displayed the savagery and dark humour typical of many of the Thunder Warriors, most notably during the Battle of Maulland Sen. After the massacre of the Thunder Warriors at Mount Ararat, he and other survivors of the Thunder Legion went into hiding. They later emerged to aid Grand Provost Marshal Uwoma Kandawire during the Palace Coup near the end of the Unification Wars out of a desire for revenge against the Emperor and an honorable death in battle. During the coup, Ushotan personally battled Captain-General Valdor and for a time managed to hold his own against the Chief Custodian. However, in the end Ushotan was struck down, and as he lay dying he remarked that he pitied the captain-general, for while while Ushotan had lived only a short life, he nonetheless had lived as a true Human, at least for a time, while Valdor was void of all emotions or Humanity save duty since he had been genetically-engineered almost since birth. Valdor agreed with Ushotan's assessment before executing him to end the dying warrior's agony.



Warhammer 40,000 Grim Dark Lore Part 5 – Unity


  • Codex: Adeptus Custodes (8th Edition), pg. 9
  • The Horus Heresy - Book One: Betrayal (Forge World Series) by Alan Bligh, pp. 26-27, 85
  • The Horus Heresy - Book Seven: Inferno (Forge World Series) by Alan Bligh, pg. 113
  • Warhammer 40,000 Compilation (1st Edition), pp. 19-20
  • The Outcast Dead (Novel) by Graham McNeill
  • The Solar War (Novel) by John French, Ch. 15
  • Dreams of Unity (Short Story) by Nick Kyme
  • Valdor: Birth of the Imperium (Novel) by Chris Wraight, Chs. 5, 15
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Warhammer 40,000 Overview Grim Dark Lore Teaser TrailerPart 1: ExodusPart 2: The Golden AgePart 3: Old NightPart 4: Rise of the EmperorPart 5: UnityPart 6: Lords of MarsPart 7: The Machine GodPart 8: ImperiumPart 9: The Fall of the AeldariPart 10: Gods and DaemonsPart 11: Great Crusade BeginsPart 12: The Son of StrifePart 13: Lost and FoundPart 14: A Thousand SonsPart 15: Bearer of the WordPart 16: The Perfect CityPart 17: Triumph at UllanorPart 18: Return to TerraPart 19: Council of NikaeaPart 20: Serpent in the GardenPart 21: Horus FallingPart 22: TraitorsPart 23: Folly of MagnusPart 24: Dark GambitsPart 25: HeresyPart 26: Flight of the EisensteinPart 27: MassacrePart 28: Requiem for a DreamPart 29: The SiegePart 30: Imperium InvictusPart 31: The Age of RebirthPart 32: The Rise of AbaddonPart 33: Saints and BeastsPart 34: InterregnumPart 35: Age of ApostasyPart 36: The Great DevourerPart 37: The Time of EndingPart 38: The 13th Black CrusadePart 39: ResurrectionPart 40: Indomitus