The Thousand Sons were the XV Legion of the original twenty Space Marine Legions. Their Primarch is Magnus, oft called Magnus the Red. The Legion turned traitor during the Horus Heresy, after which it relocated to Sortiarius, the Planet of Sorcerers, in the Eye of Terror, and dedicated itself to the Chaos God of change, sorcery and magic, Tzeentch. For a time it appeared that Tzeentch protected the Thousand Sons from the corruption and fragmentation that most of the other Traitor Legions underwent, but eventually the Legion went through a crisis of mutation and de-evolution, seemingly at the wish of their patron-God. Aghast at this development, their chief sorcerer, Ahriman, cast a powerful spell designed to render the Thousand Sons immune to the warping effects of Chaos. While the spell succeeded in this goal, it had an unforseen consequence of transforming the mutated Thousand Sons into little more than mystically animated suits of armour barely capable of being termed as anything more sentient than automata.
With the only surviving cognisant members being those incredibly strong in heretical psychic powers, the Thousand Sons are now a legion of ghosts led by the damned.
|Marine||Basic Data||Current Symbol|
- 1 Homeworld
- 2 History
- 3 Organisation
- 4 Geneseed
- 5 Culture
- 6 Recruitment
- 7 Noted Elements of the Thousand Sons
- 8 Additional Information
- 9 Sources
The homeworld of the Thousand Sons was Prospero, a world populated by a small commune of outcast psykers. Once a world of great beauty, it was attacked by Imperial forces utilising planet-busting weapons during the Battle of Prospero[2a], with the result that it became a blasted ruin, declared Purgatus by the Inquisition. Prospero would ultimately suffer the indignity of Imperial planetary bombardment a second time, ordered by the Inquisition in response to a large-scale gathering of Thousand Sons forces upon the planet as part of a sorcerous ritual. While the first bombardment (the one that took place during the first Battle of Prospero) ruined the planet's eco-system and tumbled all the works of both man and nature, it still left Prospero more-or-less recognisable. The second scoured the world with firestorms so intense that the surface of Prospero was turned into featureless black glass.
The Great Crusade
The Fifteenth Legion was formed on Terra, their gene-seed being created and implanted in the first legionaires during a brief resurgence of warp-storms within the boundaries of the Sol system itself. This brief warp-storm was said to have generated psychic flashpoints all across Terra's globe, resulting in outbreaks of madness, suicide and random violence. Whether it had any effect on the legion's gene-seed is doubtful, but upon learning of it years later Magnus himself considered it to be a poor omen.[3a]
At least part of the initial crop of legionaires - termed student-aspirants - were found amongst the population of the once geo-political entity known as the Achaemenid Empire. This area of Terra had been under the rule of the Emperor for at least a century at this point, and as a result had suffered little during the just-completed Wars of Unification. The Emperor himself, accompanied by a retinue of scientists, visited the region and had each and every family tested for compatibility with the Legion XV gene-seed. Those that were found suitable were taken to the gene-laboratories underneath the Himalayas to begin their transformation into Astartes. Present as one of these first student-aspirants was Ahzek Ahriman and his twin brother, Ohrmuzd.[3a] Upon completion of this process the Fifteenth Legion was used to quell what few pockets of isolated resistance to the Emperor's rule remained upon Terra, before being named the Thousand Sons by the Emperor himself and sent out into the galaxy as part of his Great Crusade.[3a] Their name is believed to originate from the first step of the Legion's creation process; for unknown (but presumably notable, if the Legion was named because of them) reasons, exactly one thousand Marines were created and trained first, with the Fifteenth brought up to full Legion numbers afterwards. There only being one thousand Thousand Sons in existence at a point in time is a fact that, tragically, would repeat itself in the future on more than one occasion...
Combat Disposition and Record
The combat disposition of the Thousand Sons during the Great Crusade can be viewed in two distinct parts; before and after the discovery of Magnus.
The Early Crusade
At the beginning of the Crusade, they fought as tenacious and energetic expanders of the Imperium, and were not considered particularly distinct from the main body of the Legiones Astartes. Five years into the Crusade however, the warriors of the legion - much to their delight - all began to spontaneously develop psychic abilities. This development however, was followed by a wave of horrific, unwilling degenerative mutations. This mutative process became referred to as the flesh-change, and was much feared by the Thousand Sons after it first appeared during the Compliance of Bezant. Most of those afflicted were secured in stasis chambers in the hope that some future cure would be found for them, and the numbers of active Thousand Sons began to dwindle as a result.[3a]
Over the next several decades some of the then-discovered primarchs found the notion of psychic mutants being allowed to exist as part of the Emperor's Crusade distasteful at best and downright impossible at worst and began to variously move for their censure or spread rumours and condemnations about them. Chief amongst these detractors were Mortarion, Rogal Dorn and Corax. As the years passed, more and more of the Thousand Sons devolved into mutantcy, while those that survived grew stronger and stronger in the use of their powers. Meanwhile, the detractors had managed to raise enough voices to empower a proposal that the Fifteenth Legion be dispanded and expunged from Imperial records altogether.[3a]
It was shortly after this that the Great Crusade arrived at Prospero and found Magnus, primarch of the Thousand Sons. The entire legion was transported to Prospero to meet their gene-sire, and there was much rejoicing even though the flesh-change had become a pandemic within their ranks. After the initial celebrations the Emperor and the main body of his fleet left Prospero, but the Thousand Sons remained behind, the numbers of them degenerating into mutantcy seeming to go completely out of control within a day of the Emperor's departure. Soon, the entire legion was afflicted. It was at this time that Magnus stepped in to save his gene-sons, enacting a mysterious procedure that was able to stabilise the genetic structure of the least-effected legionaires. At the end of the procedure, barely a thousand of the Thousand Sons lived.[3a]
With this stabilisation of the gene-seed, the Fifteenth Legion got its second chance. Recruiting from Prospero, they were able to rebuild their numbers - though would never become numerous - and return to the Great Crusade, this time led by their primarch.
While most details of how the Thousand Sons were organised before the coming of Magnus is not currently known, it is recorded that they were not considered particularly different from a typical Legiones Astartes apart from their psychic abilities (which resulted in the legion possessing the most powerful Librarians of the era[1a]). When Magnus took command, his directions (influenced by his development on Prospero, as well as Prosperine culture itself) would cause some organisational and hierarchial changes within the legion. Chapters were referred to as Fellowships within the Thousand Sons and the most of these the rebuilt legion was ever able to field numbered 10. However, at the conclusion of one particularly bloody campaign, the Thousand Sons had lost almost 900 Astartes, effectively wiping out an entire Fellowship. Rather than rebuild it, Magnus decided to reorganise and maintain the legion as one of 9 Fellowships, an organisation he referred to as the Pesedjet. Two special units were created within the legion; the elite Scarab Occult Terminators and the Hidden Ones of the Scout Auxillia. The legion's command structure was adapted to include Prosperine philosphy in the form of the Rehati (the coven of Magnus), a second command-track in which the legion's senior officers were ranked according to psychic ability and influence [3b]
The resurgent Thousand Sons brought their fair share of worlds into compliance with the Imperium of Man, and as such their main method of victory (diplomatic guile and trickery) was not questioned by the body Imperial. However, as the Crusade entered wilder regions of space, more and more hostile forces were encountered that deployed powers similar to those that the psychic warriors of the Thousand Sons wielded. This event, alongwith the ever-present rumours of 'withcraft' and 'sorcery' surroundng the legion, resulted in Mortarion once more raising his voice in condemnation of the Thousand Sons.[1a] This time he was joined by Leman Russ, whose long-held distrust of the legion came to a head after he witnessed the return of the flesh-change in the Thousand Sons during a joint action on the world of Shrike.[3c] It was decided that Magnus and his legion would be called to account, and the whole matter of Astartes employing psychic powers at all would be ruled upon. This event was known as the Council of Nikea, and at it - after much deliberation - the Emperor announced that no Astartes must ever again employ the use of psychic powers, upon pain of destruction visited upon them by the Emperor himself.[3d]
Stunned, the Thousand Sons effectively withdrew from the Crusade, returning to Prospero. It was during the period that followed that Magnus discerned the approach of the Horus Heresy and employed both his own powers and that of his senior legionaires to try to save his brother's soul. Failing, he once again marshalled the powers available to him and attempted to psychically warn the Emperor of his favourite son's betrayal. News of this sanction fleet, meanwhile, had previously reached the ears of the now-corrupted Horus himself. Sensing an opportunity, the Warmaster contacted Leman Russ, commander of the fleet, during the trip to Prospero. Speaking with his brother, he was able to convince him that "to return Magnus to Terra would be a waste of time and effort". Horus confirmed to his traitorous council of war that he believed this interjection of his into the Emperor's own decree would result in Magnus never leaving Prospero alive. This action, which went so catastrophically wrong, would doom the Thousand Sons as, in accord with the Judgement of Nikea, the Emperor visited destruction upon Magnus and the Thousand Sons in the form of Leman Russ and his Space Wolves.Magnus had realised his grave mistake in warning the Emperor in the method he chose, and had also been confronted with the stark reality that he was not as in control of the warp or his powers as he thought. Additionally, a power of the warp had spoken to him, revealing to him that Magnus had been its pawn since the time it had helped him save his legion from the flesh-change...and perhaps even long before that. Tizca (the only surviving city on the planet) for a period of time before they were eventually pushed back, the assault of the Space Wolves led by their primarch, as well as forces from the Sisters of Silence and the Adeptus Custodes proving too much. Magnus eventually joined the battle when it appeared that the final moment of extermination for his legion had arrived. Leman Russ engaged Magnus in a devastating duel in which the Russ was ultimately victorious. In response Magnus finally, consciously gave in to the daemonic voice that had been tempting him and invoked ancient sorceries in order to escape Prospero with the remnants of his legion. In the Eye of Terror, a Daemon World had been prepared for them by their new patron.[3e]
The Horus Heresy
Having been thus deliberately removed from the board by the machinations of Chaos[2b], the Thousand Sons played no part in the birth of the Horus Heresy. In fact, exactly when and why they chose to ally themselves with Horus and his traitorous rebellion is not clear, although it is believed that their chief motivation was to gain sanctuary and protection from further Imperial attack. Of course, considering how Tzeentch had orchestrated events so far, it is likely that they had little choice in the matter at all.
After their escape from Prospero, the Thousand Sons discovered that - once again - they had been reduced to only around one thousand living members.[3j] Their actions during the bulk of the Heresy are not currently known, though a portion of the Legion did engage the Space Wolves at the Battle of Yarant. When Horus's forces fell on Terra itself some years later, Magnus and the Thousand Sons were with him. Noted to be a very small contingent of the Chaos forces, the Thousand Sons contented themselves with summoning daemonic reinforcements and casting supporting spells rather than engaging in pitched battle for most of the Siege of Terra. However, once the outer walls of the Imperial Palace had been breached, the Thousand Sons found themselves required to break down the final wards and fortifications of the inner palace itself. Advancing to the Ultimate Gate, part of the legion held off Imperial counter-attacks while the senior sorcerers attempted to destroy the defences with psychic power and sorcerous ritual. This assault came to naught however, as a contingent of Imperial Fists led by Rogal Dorn arrived in the combat zone and drove the Thousand Sons off at much the same time as the Emperor himself directed the surviving Librarians of the Blood Angels and Imperial Fists to block the attacks of the Thousand Sons sorcerers.
The Thousand Sons retreated from Terra after the death of Horus alongside the other Chaos forces, before using their sorcerous powers to open a warp route that would transport their fleet directly to the Planet of Sorcerers.
Horus Heresy Aftermath
The dedication to the Chaos God Tzeentch resulted in several changes to the organisation of the legion, but had little direct effect on their combat doctrine. Previously known to avoid close combat in favour of psychic trickery and the use of ranged weaponry, their development into a legion of Chaos Sorcerers and the effect of the Rubric of Ahriman only increased reliance on this approach. Those marines affected by the Rubric are used to anchor an attack's firepower, while the sorcerers deploy their psychic powers, the whole event orchestrated in accordance with a previously constructed plan of deceit or guile. While showing no overt favouring of vehicles or heavy armour, the loyalist Thousand Sons did appear to deploy significant Legio Cybernetica assets in battle, although, in a fore-echo of what would come to pass with the use of Rubric Marines, they psychically controlled the robots to act as a mobile bulwark, rather than letting them operate as normal.[3h] The transition into a Chaos Legion did little to change the Thousand Sons' lack of interest in vehicular or heavy armour support; the discipline of machinery is one that most Sorcerers apparently care little for...although now and again one will take enough of an interest to produce something unusual. The existing Legion stock of vehicles and equipment has rarely been remarked upon since the end of the Thousand Sons' Imperial loyalty (indeed, it is not actually known if the Legion managed to retain anything other than those Legionaries who were transported from Prospero to the Planet of Sorcerers), but it is known that they sometimes scavenge or steal such items during raids. However, as the Thousand Sons show markedly little interest in properly maintaining their traditional armoury, these repurposed goods never last long and certainly do not appear in large numbers.
While they avoided dissolution as a legion for some time, the Thousand Sons now only seem to operate abroad as small warbands. These warbands are said to seek out conglomerations of psykers, or traces of sorcerous techniques using artefacts known as Seer Stones. Whilst the plans of the Thousand Sons are never easy to discern, being chosen as Tzeentch's favoured agents results in the actions of their warbands being varied and often curious; by raiding a particular planet, location or killing even a single, specific individual, the manipulations of Tzeentch are furthered. The most well-known of these warbands is the Prodigal Sons warband led by Ahriman.[9a]
The Rubric of Ahriman
With the embrace of Chaos, comes mutation. Once the Thousand Sons had retreated back to the Planet of Sorcerers within the Eye of Terror members of the legion began to suffer the flesh-change; horrendous physical mutations, their bodies and minds twisted in ways only Chaos can achieve. Although some dedicated Tzeentch worshippers saw these changes as a sign of their god’s favour, those of higher understanding knew better, and decided that the Thousand Sons' search for enlightenment and knowledge could not end in the dreaded transformations they would inevitably suffer. Ahriman, once Chief Librarian of the Legion, and second only to Magnus in power, united a conclave of his most trusted sorcerers, and together they cast a spell, known as the Rubric of Ahriman, of tremendous magnitude that would save the legion from the fate of mutation. The results were not what Ahriman expected...but he was satisfied with them none the less. The Thousand Sons were now safe from the taint of chaos, but at a terrible price. Those untouched by the flesh change had their psychic powers greatly strengthened, but those who had already mutated had their physical bodies reduced to dust and their animate spirits damned to live inside their armour forever. Most of the legion were therfore changed into Rubric Marines; little more than mindless automatons. When Magnus heard about the terrible failure, he banished Ahriman and his group from the Planet of the Sorcerers, and now they wander through the Eye of Terror and beyond, still pursuing magical knowledge and seeking arcane artefacts. Ahriman’s current goal is to enter the Black Library of the Eldar, and rumour has it that if he succeeds in his quest, his power will grow beyond imagination.
After the destruction of Prospero at their hands, the Thousand Sons have been long time arch-enemies with the Space Wolves chapter. They have tried several times to uproot and destroy the Wolves, ranging from a full-scale invasion of the Space Wolves' homeworld of Fenris to plots such as those spearheaded by the sorcerer Madox.[4a]
This vendetta would have an irrevocable effect upon the legion. The Thousand Sons had largely retained their legion organisation and structure after the Heresy, even raising and maintaining a large body of mortal troops they referred to as Spireguard in an echo of the Crusade-era Imperial Army regiments of Prospero. However, the last known act of the Thousand Sons as a legion was the Battle of the Fang, in which Magnus committed almost all of their remaining assets. At that time, there were approximately 700 members of the Thousand Sons left (not including the coven of Ahriman)[12a]. Their defeat resulted in the loss of several of the remaining senior legion members, several squads of Rubric Marines, much of their fleet and nearly all of their mortal units.
See main article - Notable Battles of the Thousand Sons
The Great Crusade
- ???.M30 - Terra - Pacification of the Boeotian Lowlands.
- ???.M30 - The Acceredine Defiance - One of the XV Legion's first engagements after its foundation. The Acceredine Enclave on the world of Castus is defeated by the 1st Brigade of the 2nd Regiment of the XV Legion and troops of the Imperial Army Auxiliary.[38h]
- ???.M30 - Ostratis - Compliance Action. The first Millennial of the III Legion withdraw their ships when a company of the XV Legion joined the mustering to takethe colonies of the Cyn Stars[38f]
- ???.M30 - Colgren Campaign alongside the Dusk Raiders, who refused to look at, listen to or speak to any of the Thousand Sons, dealing only through intermediaries and servitors[38f]
- ???.M30 - Necordo - Compliance Action. Two hundred warrior lead by Captain Ohrmuzd subdue the planet of Necordo in only six hours.[38f]
- ???.M30 - Rout of Megorania - The now lost Legio Lacrimae gives oaths of perpetual kinship to the Thousand Sons for driving back a force of countless Orks from their crippled Titans.[38f]
- 823.M30 - Bezant - The Flesh Change manifests for the first time.[38c]
- ???.M30 - Valnum - Compliance Action. Captain Ohrmuzd leads only sixty legionaries to the plains of Valnum. They defeat the entire House Cratax in a battle lasted for five hundred seconds, losing only three warriors. The planet is renamed 72-9.[38h]
- ???.M30 - Mih'savoh - Compliance Action. Part of the Priosa Campaign. Battle happened a decade before the re-unification with the Primarch Magnus.[38l]
- ???.M30 - The Kamenka Troika - Extermination of Greenskin infestation. Loss of 873 Astartes; Legion reorganised as a result. [3h]
- ???.M30 - Seristanus Campaign[38d]
- ???.M30 - Relief of Keene's Landing[38g]
- ???.M30 - Last Stand on Rakotis[38g]
- ???.M30 - The Turning of the Golden Apostles - Compliance Action. Magnus leads a force made up of five Circles from three different Fellowships against the Golden Apostles, a string of star systems strung between the Sol system and the outer reaches of the galactic core.[38i]
- ???.M30 - Cazhat - Compliance Action. A detachment of the Fifth Fellowship attached to the 493rd Expeditionary Fleet commanded by Shai-Captain Tachus Makt take the desert world of Cazhar without firing a single shot.[38j]
- ???.M30 - 28-16/Aghoru - Compliance Action. Compliance achieved by diplomacy; secondary combat against apparent warp corruption.[3k]
- 999.M30 - Ark Reach Cluster - Compliance Action. Compliance achieved in concert with forces of the Space Wolves and the Word Bearers. The return of the flesh-change occurred at the conclusion of this campaign.[3l][38b]
The Horus Heresy
- 004-005.M31 - The Burning of Prospero; defence of the legion homeworld against the Space Wolves; defeated.[3e]
- 004.M31 - Maktor VIII. Even before news of Prospero's destruction, 300 veterans of the Seventh Fellowship are abandoned to their deaths during the assault on Maktor VIII by the Imperial Fists.[38e]
- ???.M31 - The Battle of Yarant; Legion elements ally with Traitor forces in an attempt to exterminate the Space Wolves; defeated.
- 014.M31 - The Siege of the Emperor's Palace. Took part in the Chaos grand assault; defeated.
- ???.M31 - Kha'Sherhan warband allies with Ezekyle Abaddon to destroy the clone of Horus.[22c]
- ???.M31 - Garm - Fought the Space Wolves in the aftermath of the Horus Heresy; driven off.[10a]
- ???.M32 - The Battle of the Fang. Full scale planetary invasion of the Space Wolves' homeworld; defeated.
- 112.M33 - The Feral War; Rubric Marines left by Ahriman destroy an Adeptus Mechanicus and Relictors force on the Feral World Aggaros.
- 579.M37 - The War in the Webway; A coven of Thousand Sons Sorcerers attempt to gain access to Commorragh.
- ???.M41 - Calliope - The harvesting of the planets souls, overseen by Ahriman
- ???.M41 - Dianixis - The destruction of the planet, overseen by Ahriman
- ???.M41 - Etiamnun III - The warband of Mordant Hex gains access to the Eldar webway.
- ???.M41 - Arcadia - Ahriman and the Prodigal Sons plunder a Harlequin-guarded library amidst Blood Raven interference.[9b]
- ???.M41 - Issajur - Sorcerer Mordant Hex battles the Space Wolves.
- ???.M41 - Garm - Attempted mass resurrection of deceased Thousand Sons; plan almost totally foiled by the actions of the Space Wolves.[10b]
- 999.M41 - The Siege of the Fenris System. Magnus the Red reappears at the head of a massive invasion of Fenris. Though Magnus was banished back to the Warp by Logan Grimnar and the Grey Knights and the Thousand Sons and their Daemonic allies seemingly defeated, in truth this was part of an elaborate plan by Magnus to transport the Planet of the Sorcerers to the Materium over Prospero. A giant Warp Rift accompanies it.
- 999.M41 - 13th Black Crusade - Thousand Sons fighting alongside Abaddon the Despoiler invade territory near Prospero. Ahriman and the Prodigal Sons also attempt to raid the Eldar Black Library.
- 999.M41 - The War in the Labyrinth. Ahriman battles the Ynnari in the Webway.
- ~999.M41 - The Terran Crusade - Magnus leads the Thousand Sons against the reborn Roboute Guilliman and his Eldar allies, temporarily trapping them in the Maelstrom. Magnus and his warriors eventually chase Guilliman to Luna, engaging in a fierce battle on the moon until the Daemon Primarch is forced back into the Webway.
Magnus placed great emphasis on ensuring that legion officers could operate independently from him, going to lengths to ensure they were taught all that he believed they would need to succeed at command, including otherworldly skills. Before the Heresy the individual Thousand Sons squads were led not by established veteran warriors, but by those who showed the most psychic potential. These junior officers were also effectively apprenticed to more experienced officers for cult training. As a result of the emphasis on leaders having strong psychic ability, senior officers of the legion typically became considerably experienced in both typical battlefield combat and in the use of their powers..
Always a numerically small legion, the Thousand Sons rarely ever took to the field in great numbers. They would normally operate in small detachments, whose leader could effectively hold much more independent authority than officers in comparable positions in other Legions. With the events following the Heresy, this habit has become more pronounced.
Before the Heresy, the Thousand Sons operated several Fellowships roughly equivalent to Companies. While there were originally ten, after the events in the Kamenka Troika the legion was reorganised into nine Fellowships. Each Fellowship was led by a powerful Psyker.[3h] Spread out among these Fellowships were several Cults that specialized in different Psychic disciplines.[3i]
In addition to the Fellowships three Red Orders were also fielded by the Legion before the Heresy. These Orders were more devoted to military matters rather than psychic craft or knowledge. The three orders were the Order of Ruin, known as the Unmakers, which specialized in siegecraft and logistics. The second was the Order of the Jackal, known as the Measure of Life and Death, which operated the Legion's Dreadnoughts and Khenetai Occult. The third was the Order of Blindness, known as the Hidden Ones, which fell under the command of Amon and operated the Hidden Ones and Ammitara Occult of the Legion.[38a]
At the core of the war assemblies of the Thousand Sons are the thrallbands. These primarily consist of a champion known as a Magister and up to nine thralls, each a lesser Sorcerer-champion of Tzeentch. This cabalistic gathering usually manifests as an Exalted Sorcerer and nine Aspiring Sorcerers – or Scarab Occult Sorcerers – who lead the Rubric Marines and Scarab Occult Terminators into battle. In the rarest thrallbands, the thralls might instead be powerful Sorcerers or Exalted Sorcerers themselves. The Exalted Sorcerers and Daemon Princes who rule the Silver Towers each command many of these thrallbands, which may be gathered together into hundreds-strong task forces called Exalted Thrallbands. Their followers comprise the raiding forces through which Tzeentch enacts some of his most violent schemes upon the galaxy. While the warbands of Tzeentch’s champions manifest in countless ways, the sorcerous thrallbands of the Thousand Sons are the most favored by the Changer of the Ways. Each thrallband is bolstered by the mutated warrior auxiliaries of the Planet of the Sorcerers, or by Chaos Cultist forces drawn from the Imperium. In addition, the Legion maintains a small number of tanks and Daemon Engines. Some Space Marine equipment is captured during their raids, but as very few of these weapons or vehicles are properly maintained, they rarely last for long and so are never numerous.
While Magnus himself remains the ruler of the Planet of the Sorcerers, he is increasingly aloof with the affairs of the Materium and is spending much of his attention waging the Great Game of the Ruinous Powers.[22a] Thus since the events of the Heresy the Thousand Sons have largely operated as independent warbands under the control of Sorcerers.
As befits the genic offspring of such a colossal psychic mutant as Magnus, the geneseed of the Thousand Sons appeared to ensure the development of psychic ability. It also appeared to bring with it an unavoidable fate of physical de-evolution, but it is unknown exactly what influence Tzeentch had on the development of the Thousand Sons and their geneseed and from what point this influence began. The Flesh-Change as this de-evolution was known, was a major threat to the Legion that manifested when its members used their psychic abilities. When overcome by the Flesh-Change, a member of the Thousand Sons would rapidly mutate into a hideous beast resembling a Chaos Spawn. Due to its psychic nature, the Flesh-Change was contagious and epidemics of it were a constant terror among the Legion. Magnus and others within the Thousand Sons worked diligently to find a cure for the Flesh-Change, and it is implied that Magnus may have gained the aid of Tzeentch to suppress it. However ultimately, no cure could be found and during the Great Crusade the Thousand Sons suffered a slow death from its gene-seed flaw.
Regardless, when the Rubric of Ahriman took hold of the legion, most of their geneseed was destroyed. The only viable sources now known of are the surviving sorcerers of the Thousand Sons, powerful psykers who are so invested of the powers of the warp that the condition of their geneseed and the effects it would have upon someone implanted with it can only be guessed at.
For the Thousand Sons, knowledge is power, and the most knowledgable the most powerful. Arising from the origins of their first recruits and being driven by the early legion's need to discover a cure for the flesh-change and gain deeper understanding and control of their psychic abilities, these linked beliefs resulted in two major cultural factors developing in the Thousand Sons; veneration of the text and veneration of their Primarch.
As a result, the Thousand Sons, while sworn to the Emperor and the Imperium in word and duty, found that at the moment of testing, their loyalty to their primarch and their desire to preserve their acquired knowledge was enough to lead them down the path of damnation.
The Pursuit of Knowledge
The legion's desire to learn how to control their powers developed into a hunger for any and all knowledge. Driven from an origin of self-interest, their desire to know as much as possible and master every discipline available to learn caused them to seek shortcuts or explore morally perilous paths, especially once Magnus and his own insatiable hunger for knowledge encouraged them to progress from simple scholarship into the practice of sorcerous techniques. As a result, they have long held every record of information as a valuable item in itself, as well as a resources to be drained. Ahriman in particular has, since the Heresy, dedicated himself to this desire seemingly above loyalty to his primarch and even to Chaos itself.
While the Thousand Sons have an interest in all forms of knowledge, they particularly pursue items or places that may hold sorcerous power or reference arcane secrets. As a result, it is not unusual at all for a Thousand Sons warband to raid a museum, library or private art collection rather than a military target. And while many Legions sponsor Chaos-worshipping cults, the Thousand Sons tend to use theirs not to overthrow or destabilise Imperial power, but more rather as collectors of items and people they are interested in; much to the chagrin of cult leaders, as when a Thousand Sons warband finally answers a summons, they tend to simply leave with the cult's artefacts and best sorcerous practitioners not long after.
The Cults of the Thousand Sons
Every legion venerated their primarch in some regard, but to the Thousand Sons Magnus was their literal saviour. With his arrival they were not only (apparently) saved from the horrors of physical degredation but also presented with the person who could teach them how to master their developing psychic abilities. Drawing from his experiences on Prospero, Magnus instituted his Cult system within his legion, five teaching institutions that would allow his warrior-scholars to expand their knowledge, principally from him, at his position as master of all the cults; the rank of Magus. From this position atop a pyramidal teaching structure Magnus was able to direct and control his legion's psychic and philosophical development; as the most knowledgeable, powerful and as their genetic forefather and saviour, all Thousand Sons looked to him for example and guidance.[3f]
All members of the legion were cult members and outside their military rankings, would most likely associate with their fellow cult members in their own headquarters pyramids in Tizca. These cults, in tandem with Magnus' more direct teachings, promulgated the methods of control the Thousand Sons developed over their powers and came to be an essential factor of the marines' existences.[3f] The status of the formalized cult system after the Burning of Prospero is unknown.
Like all of the Legiones Astartes the Thousand Sons were initially made up of Terran marines. In the aftermath of Magnus' deal with Tzeentch to save their lives, only around a thousand of them were left. For the rest of the Crusade, the Thousand Sons recruited from Prospero, a planet of only limited population (although many of them were psychically active). As a result the Thousand Sons were never a large legion.[3m]
How the Thousand Sons currently maintain their numbers is unknown, although they have been observed carrying out an apparent resurrection ritual at least once. On this occasion the spirits of deceased Thousand Sons were summoned from the warp into mortal bodies (whether living or dead making no particular difference), bodies which then transformed themselves into reborn Thousand Sons.[10b]
Noted Elements of the Thousand Sons
Thousand Sons Armoury
- The Black Staff of Ahriman
- The Book of Magnus
- Seer Stones
- Blade of Magnus
- Crown of the Crimson King
- Helm of the Third Eye
- Astral Grimoire
- Photep - Battle Barge. Flagship (pre-Heresy)
- Ankhtowe - Battle Barge (pre-Heresy)
- Kymmeru - Battle Barge (pre-Heresy)
- Scion of Prospero - Battle Barge (pre-Heresy)
- Sekhemra - Strike Cruiser (pre-heresy)
- Waning Moon - Strike Cruiser (pre-Heresy)
- Geometric - Destroyer (pre-Heresy)[14a]
- Portent of the Western Dawn - Strike Cruiser (pre-Heresy)[38k]
- Herumon - Flagship (post-Heresy)
- Phosis T'Kar - Planet Scourer (post-Heresy)
- Tlaloc - Cruiser; vessel of Iskandar Khayon [22b]
- Silver Towers of Tzeentch (post-Heresy)
- The Unyielding - Unknown; flagship of the Chaos Lord Sektoth (post-Heresy)
- Magnus - Primarch of the Thousand Sons [3g]
- Ahzek Ahriman - Chief Librarian, Captain of the 1st Fellowship and Magister Templi of the Corvidae [3g]
- Phosis T'Kar - Captain of the 2nd Fellowship and Magister Templi of the Raptora [3g]
- Hathor Maat - Captain of the 3rd Fellowship and Magister Templi of the Pavoni [3g]
- Menes Kalliston - Captain of the 4th Fellowship[14a]
- Baleq Uthizzar - Captain of the 5th Fellowship and Magister Templi of the Athanaeans [3g]
- Khalophis - Captain of the 6th Fellowship and Magister Templi of the Pyrae [3g]
- Phael Toron - Captain of the 7th Fellowship [3g]
- Auramagma - Captain of the 8th Fellowship [3g]
- Amon - Captain of the 9th Fellowship and Equerry to Magnus [3g]
- Iskandar Khayon - Captain[22a]
- Ankhu Anen - Guardian of the Great Library [3g]
- Atharva - Adeptus Exemptus, legion emissary to the Crusader Host
- Revuel Arvida - Sergeant 
- Mhotep - Sergeant & Fleet Captain, the Waning Moon [5a]
- Hedara Promalac - Commander of ha heavy support squad, then one the nine Guardians of the House of the Jackal.[38g]
- Penthu Daast - Primus Medicae, Heroditine Circle of the Legion Apotecharion, 8th Fellowship.[38m]
- Magnus the Red - Daemon Primarch of the Thousand Sons
- Ahzek Ahriman - Sorcerer Lord, exile.
- Akhor'menet - Sorcerer
- Amon - Sorcerer Lord, exile 
- Azhtar Manutec - Sorcerer
- Herume Aphael - Sorcerer and commander during the Battle of the Fang[12b]
- Mordant Hex - Sorcerer[1a]
- Karlsen - Sorcerer [8a]
- Khadeth - Dreadnought
- Iskandar Khayon - Sorcerer Lord, sword-brother to Abbadon the Despoiler. Founding member of the Black Legion[22a]
- Khrove - Sorcerer Lord and warlord
- Madox - Sorcerer 
- Mordeghai - Sorcerer and Warband leader
- Myrath - Sorcerer
- Onoris - Helbrute
- Hakor Thrice-born - Sorcerer
- Aarthrat - Sorcerer
- Omarhotec - Sorcerer
- Daedophet - Sorcerer
- Naratt - Sorcerer
- Nezchad Aratos - Magister
- Ashur-Kai Qezremah - Sorcerer; now part of the Black Legion[22a]
- Sektoth - Chaos Lord of the Warband of Sektoth
- Seth the Gatekeeper - Warband Leader
- Atum Sum - Sorcerer
- Ahmuz Temekh - Sorcerer and commander during the Battle of the Fang[12b]
- Tolbek - Member of the Brotherhood of Dust[26b]
Notable Known Warbands
- Blades Of Magnus
- Brotherhood of Dust - the warband of Amon[26a]
- Brothers of Retaliation - the warband of Laudren Thalarn
- Crimson Sons
- Grand Order of Hermetic Blades
- Silver Sons
- Kha'Sherhan - the warband of Iskandar Khayon
- Prism of Fate
- Prodigal Sons - the warband of Ahriman[9a]
- Sectai Prosperine
- Seth's Chosen - the warband of Seth the Gatekeeper
- Tizcan Host
- Warband of Sektoth - the warband of Sektoth
- Warp Gheists
- Rubric Marine
- Scarab Occult (Heresy-era)
- Hidden Ones (Heresy-era)
- Ammitara Occult (Heresy-era)
- Khenetai Occult (Heresy-era)
- Osiron Dreadnought
- Castellax-Achea Class Robot
- Cults of the Thousand Sons
- Rubric Marines
- Chaos Space Marine Legions and Warbands (List)
- Space Marine Forces (List)
Trivia and Notes
A detailed explanation of the term "Trivia" and "Varia" as used in the Lexicanum can be found here.
- The Achaemenid Empire, the legion's first recruiting ground on Terra, is a reference to the historical Achaemenid Empire, ie. the Persian Empire at the time of Classical Greece.
- The Thousand Sons being used to pacify Boeotia during the Unification of Terra is a reference to the the Greco-Persian wars.
- Ahriman and Ohrmuzd are the names of the evil and good deities, respectively, of Zoroastrianism.
- Prospero is the name of the exiled noble, scholar and sorcerer forced to cast aside his works and turn his back on magic in Shakespeare's The Tempest.
- In Egyptian mythology a pesedjet - Magnus' term for the structure of his legion - was a grouping of nine deities.
- In older source material - pre-dating the addition of the Rubric of Ahriman to the background - not all Thousand Sons were said to be psykers, though all had sorcerous knowledge and various minor levels of magic ability. They operated in effectively the same way - individuals of great power supported by line troops - but for completely different reasons. In addition, earlier edition models and artwork made much use of the trope of Tzeentch gifting physical mutations upon his followers. This trope vanished from such material with the introductions of the Thousand Sons' distinctive visual design, their own unique miniatures and the concept of Rubric Marines, but has since been reincorporated into the background as the flesh-change.
The design of the Thousand Sons has evolved over the history of the background. The first iteration saw extensive use of 'mutated' body designs such as elongated limbs or 'flamer' parts. Additionally, the legion icon of the Thousand Sons was originally a capital letter 'M' (the Roman numeral for one thousand). At some point in first edition this design began to be revised into a more ornate, un-mutated appearance, with an ourobouros symbol replacing the 'M'. When the Thousand Sons background was established in second edition, the revised version became their primary design, with 'Egyptian' elements added. They have remained largely unaltered ever since, though colour weightings have occasionally changed and a 'glow' visual being depicted on both miniatures and artwork grew popular.
Tzeentch Renegade with Flamer lower half
Glow visual on miniature; note the integration of Black Legion colours and heraldry
Forge World resin Dreadnought miniature
A Horus Heresy-era marine.
|Loyalist||I - Dark Angels · V - White Scars
VI- Space Wolves · VII- Imperial Fists
IX- Blood Angels · X- Iron Hands
XIII- Ultramarines · XVIII- Salamanders
XIX- Raven Guard
|Traitor||III- Emperor's Children · IV- Iron Warriors|
VIII- Night Lords · XII- World Eaters
XIV- Death Guard · XV- Thousand Sons
XVI- Luna Wolves/Sons of Horus · XVII- Word Bearers
XX- Alpha Legion
- 1: Index Astartes III, pp.40-47
- 2: Prospero Burns by Dan Abnett
- 3: A Thousand Sons by Graham McNeill
- 3a: Chapter Twenty-Two, pp.380-388
- 3b: Chapter One, p.28, Chapter Two, p.42, Chapter Three, pp.53-55
- 3c: Chapter Thirteen, pp.235-237
- 3d: Chapter Twenty, pp.355-356
- 3e: Chapters Twenty-Five to Thirty-One
- 3f: Chapter Seventeen, pp.300-301
- 3g: Dramatis Personae
- 3h: Chapter Two
- 3i: Chapter Three
- 3j: Chapter Thirty-One
- 3k: Chapters Eight to Ten
- 3l: Chapters Eleven to Thirteen
- 3m: Chapter One
- 4:Space Wolf by William King
- 4a: Chapter Seventeen
- 5: Battle for the Abyss by Ben Counter, Dramatis Personae
- 6: Codex: Chaos Space Marines (4th Edition), pg.50
- 7: Realms of Chaos: The Lost and the Damned, pp.267-8, p.277
- 8: Warhammer 40,000: Wargear (2nd Edition)
- 8a: pp.78-80
- 9: Tempest - Blood Ravens: The Dawn of War Omnibus by C.S. Goto
- 10: Grey Hunter by William King
- 11: Ahriman: Unchanged by John French, Chapter XV
- 12: Battle of the Fang by Chris Wraight
- 13: Codex: Eye of Terror (3rd Edition), p.17
- 14: Rebirth by Chris Wraight
- 15: Black Crusade Core Rulebook, p.341
- 16: Deathwatch: First Founding, p.88
- 17: Apocalypse, p.171
- 18: Codex: Chaos Space Marines (6th Edition), p.21
- 19: The Outcast Dead by Graham McNeill, Dramatis Personae
- 20: Black Crusade preview
- 21: The First Heretic by Aaron Dembski-Bowden, Chapter 9
- 22: The Talon of Horus by Aaron Dembski-Bowden
- 23: Codex: Space Wolves (7th Edition) - Hunters of Fenris
- 24: The Masters, Bidding (Short Story) by Matthew Farrer
- 25: Imperial Armour Volume Thirteen - War Machines of the Lost and the Damned, p.102
- 26: Ahriman: Exile by John French
- 27: Warlords of the Dark Millennium: Ahriman - Dreams, Wars, and Bloodshed
- 28: White Dwarf 96 (2015) - Parade Ground: Onoris The Warmaker, Thousand Sons Helbrute
- 29: Seth The Gatekeeper - New to Redemption, Ragnar and Seth!
- 30: Seth's Chosen - New to Redemption: Redemptionists & Seth's Chosen!
- 31: False Gods (Novel), Chapter 21
- 32: White Dwarf 25 (2014) - The Battle of Valmar"
- 33: https://www.forgeworld.co.uk/en-NZ/Thousand-Sons-Achean-pattern-Armour-Upgrade-Set (last accessed 10 April 2016)
- 34: Weregeld by Gav Thorpe, Chapter Four
- 35: Codex: Dark Eldar (7th Edition) - The Three Ages of the Dark City
- 36: The Citadel Journal 33, pp. 95-96
- 37: War Zone Fenris: Wrath of Magnus - The Serpent and the Wolf
- 38: The Horus Heresy Book Seven - Inferno