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"Give me the Scout as a boy, and I'll give you the battle-brother as a man."

Veteran Scout Sergeant Dvan Skor of the Storm Wardens Chapter
Space Marine Implants chart

Chart of Space Marine gene-seed implant locations used by Apothecaries.

Gene-seed is the colloquial term used amongst the Adeptus Astartes for the genetic material that allows for the creation of the superhuman Space Marines.

The gene-seed is actually the catch-all term for those germ cells and viral machines that have been genetically-engineered to develop into the various organs that are implanted into a normal Human adolescent male to transform him into a transhuman Astartes.

All of the gene-seed was originally crafted in the 30th Millennium by the Emperor of Mankind and the scientists of the Biotechnical Division in His gene-laboratories deep beneath the Himalazian (Himalayan) Mountains for this purpose using the genomes of each of the 20 primarchs as a template.

The term is most commonly used to refer to the contents of the Astartes Progenoid Glands which must be harvested by a Space Marine Apothecary so that its genetic material can be used to create a new generation of Astartes. There are 19 types of gene-seed, each corresponding to one of the 19 specialised organs implanted into the body of a Human male to create a Space Marine.

As many of these implants are neural in nature, it is important to note that for many of these implantations the subject must be awake for the surgery and the mind cannot be dulled by the use of painkillers.

Many of these organs are cultured in vitro from the gene-seed, whilst others require that the gene-seed be injected into the Aspirant's body and then grow into a new organ using the implantee's own physiological processes. All Space Marine Chapters use the gene-seed organs to unleash and control the metabolic processes that transform an ordinary mortal into a Space Marine.


The Anatomie Astartes, a schematic of the order and location of Astartes gene-seed organ implants.

The gene-seed itself is encoded with all the genetic information needed to reshape ordinary Human cell clusters into the special organs Space Marines possess in those instances where they are not directly implanted after being cultured outside the body.

The gene-seed contains genetically-engineered viral machines which rebuild the male Human body according to the biological template contained within it and originally crafted by the scientific acumen of the Emperor.

However, even from the beginning of the Astartes' existence, there has never been a set, standardised method to activate these transformative functions of the gene-seed. As a result, each Chapter may pursue its own methods and rituals surrounding the process of creating a new Space Marine.

During the First Founding of the 30th Millennium when the 20 Space Marine Legions were created, the process was still highly experimental and many different ways of controlling and managing the transformation from mortal man into Astartes were tried.

This led to the Space Wolves using the ritual known as Blooding, the Imperial Fists using the process known as the Hand of Faith, the White Scars conducting the Rites of the Risen Moon and the Blood Angels using the ritual of Insanguination.

Gene-Seed Implants

Neophyte Implants

A neophyte undergoes the painful transformation into a Space Marine.

Since the First Founding, the Chapters of the Adeptus Astartes have lost the ability to engineer new gene-seed or implant Astartes organs from scratch. They also do not often possess enough stable genetic material to directly culture all 19 implants available to their Chapter due to the loss or rampant mutation of the gene-seed for one or more organs.

All Chapters are different, but the "purest" Chapters in this respect are the Grey Knights, the Ultramarines, and the Dark Angels, who have maintained a large enough supply of stable gene-seed to develop all 19 fully functioning Astartes organ implants. It is for this reason that the Ultramarines and the Dark Angels have more Successor Chapters than any of the other First Founding Chapters.

Space Marine Stages Initiation

Magos Biologis chart displaying the stages in Space Marine initiation.

However, all known Astartes Chapters possess the gene-seed required to culture the Black Carapace, as this is necessary for a Space Marine to use his power armour, and the Progenoid Glands, without which the Chapter would be incapable of creating new Astartes.

The implantation of new gene-seed or gene-seed organs has over the centuries turned into a near-religious ritual. Some Astartes will need further operations after the initial implantation procedure to fix imbalances caused by poor surgery or their own body's poor metabolic adjustment to the hormonal and physical changes initiated by the implants.

Gene-seed Organs

  • Secondary Heart - The Secondary Heart, also called the Maintainer, is the first and least difficult of the 19 Astartes gene-seed organ implants a Space Marine neophyte receives to transform him into a full Astartes. It resembles a smaller version of the Human heart and is implanted in the chest cavity and connected to the rest of the neophyte's circulatory and pulmonary systems near the original heart. Its function is to enhance the performance of an Astartes by supplying more oxygen and nutrients to the muscles by increasing blood flow well-beyond that capable for even the most fit normal Human being. The Secondary Heart can often save an Astartes' life in combat. In the event of combat damage to or failure of the Space Marine's original heart, the Secondary Heart is usually capable of pumping enough blood through the Astartes' circulatory system to maintain survival until he can be treated by the Chapter's Apothecaries.
  • Ossmodula - The Ossmodula, also called the Ironheart, is the 2nd gene-seed organ received by a Space Marine neophyte. This implant, surgically placed alongside the neophyte's pituitary gland at the base of the brain, thus becoming a part of the Space Marine's endocrine system, secretes a specially engineered form of Human growth hormone. When the effects of this hormone are combined with a diet laced with microscopic ceramic-based minerals, they act to synthesise the rapid growth of an Astartes' skeleto-muscular system which results in an Astartes' superhuman strength and massive size compared to a baseline Human male. Two Terran years after the surgery to implant the Ossmodula is completed, the neophyte Space Marine's skeleton will be larger and exponentially stronger than a normal man's with growth having topped out at around 7-7.5 Terran feet (2.1 - 2.3 metres) in height with an equivalent amount of skeleto-muscular mass. During this time the rib cage will fuse into a solid mass of bullet-proof, interlaced bone plates. The resulting structure protects the Space Marine's organs from damage in a way the normal Human skeleton never could, though at the price of producing greater difficulties for the Chapter's Apothecaries when they must perform surgeries on a Space Marine's body cavity.
  • Biscopea - The Biscopea, also called the Forge of Strength, is the 3rd gene-seed organ to be implanted. It enhances a Space Marine's physical combat ability and survivability to superhuman levels should he live to become a full Astartes of a Space Marine Chapter. This organ is implanted into the chest cavity. It is small, approximately spherical and, like the Ossmodula, its primary action is hormonal. The presence of the Biscopea stimulates muscle growth throughout the body, greatly increasing a Space Marine's physical strength. It can be implanted at the same time as the first two organs, the Secondary Heart and the Ossmodula, generally between the 10th and 12th standard years of age of the neophyte.
  • Haemastamen - The Haemastamen, also known as the Blood Maker, is the 4th gene-seed organ. Once implanted into a main blood vessel like the aorta, femoral artery or the vena cava, the Haemastamen alters an Astartes' blood's biochemical composition to carry oxygen and nutrients more efficiently. The actions of the Haemastamen turn a Space Marine's blood a brighter shade of red than that of normal Humans because of its greatly increased oxygen-carrying capacity. It also acts to biochemically regulate the actions of the 2nd and 3rd gene-seed implants, the Ossmodula and Biscopea.
  • Larraman's Organ - Larraman's Organ, also called the Healer, is the 5th gene-seed organ. Shaped like the Human liver but only the size of a golf ball, this gene-seed organ is placed within the chest cavity and manufactures the synthetic biological cells known as Larraman Cells that were named after one of the researchers in the Emperor of Mankind's gene-laboratories on Terra where the gene-seed for the first Space Marines was created under the Emperor's direction from His primarchs' DNA. These biosynthetic cells serve the same physiological purpose for an Astartes as the normal Human body's platelets, serving to clot the blood lost from wounds, but act faster, more efficiently and more effectively. When a Space Marine is wounded and incurs blood loss, Larraman Cells are released by his circulatory system, attached to the body's normal leukocytes (white blood cells). At the site of the injury, they form scar tissue in a matter of seconds, effectively preventing massive blood loss and infection of the wound. The action of this organ is one of the reasons that the Space Marines are seen as nearly invincible and so difficult to kill despite the terrible wounds they sometimes endure.
  • Catalepsean Node - The Catalepsean Node, also called the Unsleeping, is the 6th gene-seed organ. This is implanted into the back of the cerebrum, just above the brain stem. When deprived of sleep for a long period of time, the Catalepsean Node "cuts in" upon detecting a rise in the Astartes' stress and fatigue hormones. This allows the Astartes to consciously "switch off" sections of the brain sequentially, while remaining awake and alert. This ability comes at a price, as prolonged use of this ability can be hazardous, possibly inducing hallucinations or even psychosis. This implant bears a resemblance to an ancient scientific theory as to how cetaceans known as "Bottlenose Dolphins" "sleep": shutting off sections of their brain while remaining awake and alert through the active use of the other sections. Yet even the mighty Space Marines cannot go too long without actual rest. The longest any Space Marine has ever been on active combat duty without rest is 328 solar hours, achieved by a squad of the Crimson Fists' Kill-team during the battle against the Orks for Rynn's World.
  • Preomnor - The Preomnor, also called the Neutraliser, is the 7th gene-seed organ. The Preomnor is essentially a second or "pre-stomach" spliced into the Human digestive system above the original stomach that allows Space Marines to eat otherwise poisonous or completely indigestible materials. The Preomnor is capable of biochemically analysing ingested materials and neutralizing most known biochemical and inorganic toxins, and many others that remain unknown save for their toxic effects. Deadly poisons are either neutralised or isolated from the digestive tract by the Preomnor. The Preomnor can also be isolated from the rest of the digestive tract to deal with particularly toxic substances that a Space Marine may simply vomit back up later. Often these extracted toxins are rerouted and then molecularly stored in the Betcher's Gland for future usage by the Astartes.
  • Omophagea - The Omophagea, also called the Remembrancer, is the 8th gene-seed organ. The Omophagea is implanted into the spinal cord and then wired into the central nervous system so that it is directly attached to the cerebral cortex and to the stomach. It allows the Astartes to gain part of an individual person's or creature's memory by eating its flesh. This special organ is implanted between the thoracic vertebrae and the stomach wall and is designed to absorb information and any DNA, RNA or protein sequences related to experience or memory. This implant thus allows a Space Marine to literally "learn by eating." Four new nerve bundles are also implanted connecting the spine and the stomach wall. The Omophagea transmits the gained information to the Astartes' brain as a set of memories or experiences. This enables the Space Marine to gain information, in a survival or tactical sense, simply by eating an animal indigenous to an alien world and then experiencing some of what that creature did before its death. It is the presence of this organ that is responsible for the various flesh-eating and blood-drinking rituals for which certain Space Marine Chapters are famous, as well as giving names to Chapters such as the Blood Drinkers and Flesh Tearers. Over time, mutations in this implant's gene-seed have given some Chapters an unnatural craving for blood or flesh.
  • Multi-lung - The Multi-lung, also called the Imbiber, is the 9th gene-seed organ. The Multi-lung is a third lung implanted into an Astartes' pulmonary and circulatory systems in the chest cavity that is able to absorb oxygen from environments usually too poor in oxygen to allow normal Human respiratory functioning. Breathing is accomplished through a sphincter implanted into the trachea, allowing all three lungs to be used at full capacity. In toxic environments, a similar muscle closes off the normal lungs, thus oxygen is absorbed exclusively by the Multi-lung, which then filters out the poisonous or toxic elements. The Multi-lung has highly efficient toxin dispersal systems.
  • Occulobe - The Occulobe, also called the Eye of Vengeance, is the 10th gene-seed organ. This implant sits at the base of the brain after being implanted along the optic nerve and connected to the retina, and provides hormonal and genetic stimuli which enable a Space Marine's eyes to respond to the optic-therapy that all neophytes must undergo in their Chapter's Apothecarium. These procedures, in turn, allow the Chapter's Apothecaries to make adjustments to the growth patterns of the eyes and their light-receptive retinal cells. The result is that Space Marines have visual acuity that is far superior to that of baseline Humans and they can see in low-light conditions and near-darkness almost as well as in bright daylight.
  • Lyman's Ear - The Lyman's Ear, also called the Sentinel, is the 11th gene-seed organ. Not only does this implant's improved inner ear structure make a Space Marine immune to dizziness or motion sickness but it also allows Space Marines to consciously filter out and greatly enhance certain sounds over the capabilities of normal Human hearing. The Lyman's Ear completely replaces one of a Space Marine's original ears. It is externally indistinguishable from a normal Human ear in size and shape. Lyman's Ear is named after one of the scientists who worked in the Emperor's gene-laboratories on Terra in the 30th Millennium who aided in the project to produce the first primarchs and Astartes using the Emperor's own genome as the starting point.
  • Sus-an Membrane - The Sus-an Membrane, also called the Hibernator, is the 12th gene-seed organ. Initially implanted within a neophyte's cranium, this membrane eventually merges with the recipient's cerebrum, becoming a full part of his neural architecture. The organ's functions are ineffective without follow-up chemical therapy and training by a Chapter's Apothecaries, but with sufficient practice and instruction a Space Marine can use this implant to enter a state of suspended animation, consciously or as an automatic reaction to extreme trauma, keeping the Space Marine alive for Terran years, even if he has suffered otherwise mortal wounds. Only the appropriate chemical therapy or hypnotic auto-suggestion can revive a Space Marine from this state. The longest recorded period spent in suspended animation was undertaken by Battle-Brother Silas Err of the Dark Angels Chapter, who was revived after 567 standard years in Sus-an hibernation.
  • Melanochrome - The Melanochrome, also called the Skinshield, is the 13th gene-seed organ. This hormonal implant is attached to the Human lymphatic system and controls the amount of melanin in a Space Marine's skin. Exposure to high levels of sunlight will result in the Astartes' skin naturally darkening to compensate. It also protects the Space Marine from other forms of electromagnetic radiation. Different levels of radiation cause variations of skin colour in different Chapters due to mutations in the Melanochrome organ's gene-seed. This can be related to the unusually pale skin of the Blood Angels and their Successor Chapters and the dark black skin and red eyes of the Salamanders.
  • Oolitic Kidney - The Oolitic Kidney, also known as the Purifier, is the 14th gene-seed organ. It is implanted within the new Astartes' abdominal cavity and it becomes a part of the Space Marines' excretory system, an emergency detoxification organ that allows a Space Marine to survive exposure through the respiration, tactile contact or ingestion of poisons, toxins and gases that are too powerful for even his rugged immune system to normally process without this organ's help. However, this detoxification process renders the Astartes unconscious once it begins, so it can be very dangerous if required during combat. Under normal circumstances, the Oolitic Kidney also acts as a regulatory organ for the Astartes physiology, maintaining the efficient action of the Space Marine's advanced circulatory system and the proper functioning of his other organs, implanted or natural.
  • Neuroglottis - The Neuroglottis, also called the Devourer, is the 15th gene-seed organ. It is implanted within the Astartes' upper nasal passages and after it is functioning, chewing, tasting or smelling a substance allows a Space Marine to biochemically test it for toxicity and nutritional content, essentially determining if the substance is edible or poisonous. The organ also allows the Space Marine to identify extremely subtle odours with the same fidelity as the average canine bred for tracking, allowing him to even track his quarry by smell or taste alone.
  • Mucranoid - The Mucranoid, also called the Weaver, is the 16th gene-seed organ. It is implanted within the central nervous system and responds to specific chemical stimuli in the environment, causing the Space Marine to secrete a waxy protein substance similar to mucus through his pores that seals his skin. The gland's operations must first be activated by an external chemical treatment, usually self-administered, before it will activate. Space Marines are cocooned in this way before they enter suspended animation, and the process can even protect them from the harshness of the vacuum and other extremes of temperature, particularly deeply frigid environments.
  • Betcher's Gland - The Betcher's Gland, also known as the Poison Bite, is the 17th gene-seed organ. Consisting of two glands that are implanted into multiple locations inside a Space Marine's mouth, including the inside of the lower lip, in the salivary glands or in the hard palette, these two glands working in tandem transform an Astartes' saliva into a corrosive, blinding acid when consciously triggered. This allows a Space Marine to spit a wad of corrosive acid with the effect of blinding, wounding or even killing an enemy outright. These implants' more common use is to aid in the digestion of unusually difficult or impossible things to digest, such as cellulose. In the gene-seed of several primarchs, like that of Rogal Dorn, this organ has atrophied and is no longer as effective or has simply ceased to function entirely in the Astartes of the Chapters that use those primarchs' gene-seed.
  • Progenoid Glands - The Progenoid Glands, also known simply as the Gene-Seed, are the 18th organ. Every Space Marine has a pair of these organs, one implanted in the neck and another in the chest. The organs hormonally respond to the presence of the other Astartes gene-seed implants in the body by creating germ cells with DNA identical to that of those implants through a process very similar to cellular mitosis. These germ cells grow and are stored in the Progenoid organs, much like sperm cells or egg cells are stored in the testes and ovaries of normal men and women. When properly cultured by the Apothecaries of a Space Marine Chapter, these germ cells can be gestated into each of the 19 gene-seed organs needed to create a new Space Marine. Thus, for most Astartes, their Progenoid Glands represent the only form of reproduction they will ever know, though the DNA passed on will be that of their primarch, not their own. Mature Progenoid organs can be removed and new gene-seed implants artificially cultured from them. This is the only way new implants can be created, so a Chapter depends upon its existing Space Marines to create other Space Marines. Five standard years after implantation, the Progenoid Gland in the neck contains mature gene-seed and may be removed and its germ cells harvested, while the larger chest Progenoid is not considered ready for harvesting until 10 standard years have passed. The harvesting is normally done after an Astartes' death by an Apothecary, who carries a special attachment on the mobile medical field kit he carries on his arm known as a Narthecium. This attachment is called a Reductor and it is specifically used to extract both Progenoid Glands from the body of a slain Astartes so that his gene-seed can be used to replace the Chapter's loss, the only form of true immortality that Astartes will ever know.
  • The Black Carapace - The Black Carapace, also known as the Interface, is the last and one of the most important of all the 19 gene-seed organ implants a Space Marine neophyte will receive as he is transformed from a normal, adolescent Human male into a superhuman Astartes. This neuroreactive, black organic fibrous material is implanted directly under the skin of the neophyte's torso. Points are then cut through the Carapace by an Apothecary using surgical tools that allow a Space Marine to directly interface his central nervous system with his Power Armour's cybernetic systems. After a few solar hours, the material hardens and invasive synthetic fiber bundles that will serve as connection points for neurons grow inward and interlink with the newborn Astartes' central nervous system. Note that a Space Marine needs the Black Carapace to use his Power Armour to its maximum capabilities, but the armour itself does not need this implant in order to function. The Sisters of Battle, for example, as well as some Inquisitors, also wear Power Armour. However, since their central nervous systems are not linked directly to their armour's Machine Spirit (artificial intelligence) as a Space Marine's would be, their Power Armour is markedly less efficient at providing protection or allowing them to manoeuvre in combat than that of an Astartes.

Primaris Gene-Seed

Though they now stand a step above their Firstborn Astartes brethren, all Primaris Space Marines were still created using the original gene-seed of their primarchs, like all other members of the Adeptus Astartes. Some voices within the Imperium now worry how this new type of transhuman warrior will react to the many genetic quirks and flaws found in the gene-seed of some of the more unusual Chapters, particularly given the long history of fiascoes that have resulted from attempts to alter the Emperor's original work.

In the pursuit of his attempt to improve upon the original Space Marine template, Archmagos Dominus Belisarius Cawl collected samples of the genomes of all twenty of the original primarchs, including those deemed Lost or Traitors, though the resurrected Primarch Roboute Guilliman made clear to his overeager servant that Primaris Marines were to be created only from the lines of those of his brothers who led the nine Loyalist Space Marine Legions.

It is known that in addition to the general advancements in their gene-seed, Primaris Space Marines possess three additional gene-seed implant organs compared to their Firstborn brethren and that their gene-seed is far more genetically stable than that of their forerunners.

Primaris Space Marine gene-seed has only a .001% chance of genetic deviancy from the original baseline with the passage of each generation, which makes it nearly immune to the severe genetic instability suffered by Chapters such as the Blood Angels and Space Wolves over the course of their existence.

Nearly every Space Marine created since the First Founding possesses nineteen specialised organs derived from this gene-seed. The Primaris Marines, however, are implanted with a further three additional organs. It was the Sangprimus Portum, a device containing potent genetic material originally harvested from the primarchs, that allowed for this breakthrough.

Entrusted to Cawl by Guilliman shortly after the Second Founding in the early 31st Millennium, this device resulted in a new breed of Adeptus Astartes that were deployed en masse in the Ultima Founding of ca. 999.M41.

Due to Cawl's interpretation of his orders and the millennia-spanning labour of his task -- during which Guilliman was mortally injured and suspended in stasis on Macragge -- the secrets of these new Primaris Marine organs were not released until late in the 41st Millennium.

Primaris Organs

The Primaris Space Marines possess all of the nineteen gene-seed implant organs that have been gifted to their original Firstborn Astartes brothers, as well as three more that only they possess, for a total of twenty-two. These new gifts of Belisarius Cawl's genius further enhance their transhuman status and ability to bring the Emperor's justice to a galaxy shrouded in darkness and despair. These additional implanted organs include:

  • Sinew Coils (The Steel Within) - The Primaris Space Marine's sinews are reinforced with durametallic coil-cables that can contract with incredible force, magnifying his strength as well as giving his body another layer of defence. A Primaris Space Marine can crush a man's skull in his hand, break Flak Armour to flinders, or even bite through a metal cable should the need arise.
  • Magnificat (The Amplifier) - A small, thumbnail-sized lobe that is inserted into the brain's cortex. The Magnificat secretes hormones that increase the body's growth functions whilst also intensifying the function of its other transhuman implants, especially those of the Biscopea and the Ossmodula. As a result, Primaris Astartes are even taller by a Terran foot (approximately .31 metres) and physically stronger than their Firstborn counterparts. In truth, the Magnificat is but half of the true, dual-valve Immortis Gland (the so-called "God-Maker") that the Emperor created for His primarchs. However, Archmagos Cawl could only find materials and genetic blueprints to build the Dextrophic Lobe (the right half of the Immortis Gland), while plans for the Sintarius (the left half) that would complete the original super-organ had been wholly eradicated from Imperial records of the Primarch Project. Whether this was done by the Emperor's own hand or by some nefarious source, Cawl could not tell.
  • Belisarian Furnace (The Revitaliser) - This is a dormant organ that connects to both Astartes hearts. In times of extreme stress, or should the warrior's body undergo violent, damaging trauma, it expels great bursts of self-synthesized chemicals -- a hyper-cocktail that simulates the biological action of combat stimms while also aiding in the rapid regrowth of tissue, bone and muscle. The gland then falls dormant again, and takes some time to metabolically build itself up once more for the next usage.

Canis Helix

The Canis Helix, also sometimes called "The Spirit of the Wolf," is the term for the unique mutation of the gene-seed received by the neophytes of the Space Wolves Chapter in addition to the normal gene-seed organ implants that were created using the genome of their Primarch Leman Russ.

The Canis Helix also serves as the genetic catalyst that initiates the metabolic process of transformation from a mortal man into a superhuman Astartes.

The inherent instability of this genetic material is what causes the Astartes of the Space Wolves to develop their wolf-like qualities, chief among them their extremely good sense of smell and their elongated canine fangs, which is their most identifiable physical feature.

The Canis Helix also causes the Space Wolves to grow unusual amounts of body hair throughout their lives and in some individuals is the cause of their rapid degeneration into the feral mutants known as the Wulfen.

Notable Gene-Seed Flaws

Just like normal Human germ cells, exposure to high concentrations of ionising radiation can effectively render a Space Marine "sterile" by destroying the germ cells within his Progenoids.

Over the long millennia since the Space Marine Legions were first founded, a Space Marine Chapter's gene-seed can mutate during the replication process, producing new and hitherto-unknown physiological effects in that Chapter's Space Marines or simply becoming non-functional.

Repeated exposures to the corrupting psychic energies of Chaos can also cause mutation within the gene-seed. This is why every Chapter's gene-seed is required to be monitored for mutations and genetic purity by the Tech-priests of the Adeptus Mechanicus and why every Chapter is required to tithe 5% of its gene-seed stocks at regular intervals to the Mechanicus on Mars.

This is done both to check for genetic purity and to be used to create new Space Marine Chapters if the High Lords of Terra call for a Space Marine Founding.

Genetic Flaws
First Founding Lion El'Jonson Dark Angels As the I Legion of the Space Marine Legions, the Dark Angels' gene-seed is one of the purest and least degraded of all. There are no known aberrations in the Dark Angels' gene-seed, which makes the reluctance of the High Lords of Terra to utilise it in the founding of new Chapters perplexing. The Dark Angels and their Successor Chapters, collectively known as the Unforgiven, have an unusually close bond, often working hand-in-hand with one another. But often, these Chapters have a tendency to be highly suspicious of outsiders and can appear unreasonably aloof and intransigent. Indeed, there have been a number of occasions where the Dark Angels or one of the Unforgiven have withdrawn suddenly and with no explanation from a warzone when confronted by an Inquisitor or missionary. Rumours continue to persist of nepotism and legion-building. Over time these factors have led to the Unforgiven being regarded with distrust by the wider Imperium. Despite their impeccably pure gene-seed, the Dark Angels have been passed over for many of the Foundings that have created fresh Chapters to fight the Imperium's wars. Yet from time to time, the Adeptus Terra have been forced to permit the Dark Angels another Founding, the records of which have mysteriously vanished shortly afterward. In this way, an uncertain number of Unforgiven Chapters have been created, each giving every outward appearance of fighting their own wars for the Imperium, while secretly aiding in the Dark Angels' hidden hunt.
Fulgrim Emperor's Children The III Legion's gene-seed and its conditioning produced warriors with finely sculpted physiques, a noble bearing, and finely-controlled thought processes, with psychological tendencies driven towards personal achievement and competition to prove individual superiority. The only physical abnormality registered was the occasional incidence of albinism, and a shift in iris colour to violet in some recruits.
Perturabo Iron Warriors The Iron Warriors' gene-seed produced a marked tendency towards suspicion and paranoia within the Astartes of the IV Legion but also was known to create Space Marines who were extremely intelligent and possessed naturally well-developed problem-solving abilities.
Jaghatai Khan White Scars The gene-seed of the White Scars appeared to be stable and initially displayed no aberration or mutation. However, with the introduction of genetic material from the steppes tribesmen of Mundus Planus, the genome seemed to have inherited their wild savagery and thirst for war.
Leman Russ Space Wolves Enlarged canine teeth, extreme hirsuteness and possibility of mutational degeneration into a Wulfen due to genetic incompatibility with the Canis Helix.
Rogal Dorn Imperial Fists Over time the Imperial Fists have lost the use of two of the Astartes organs: the Betcher's Gland, which allows a Space Marine to produce poisonous/acidic spittle, and the Sus-an Membrane, which allows an Astartes to enter a state of suspended animation. Battle-brothers of this Chapter also display a pathological, obsessive need to scrimshaw the bones of their dead when off-duty. The Imperial Fists and their Successor Chapters tend to display the worrying psychological traits of self-castigation for perceived failures, both real and imagined, and often make use of a device called the "Pain Glove," which encases the whole body and stimulates its pain neurons or through some other means such as flagellation. Some scions of Dorn Chapters display a unique genetic deficiency known as "Dorn's Darkness," a trance-like state that is akin to a living nightmare -- where the afflicted battle-brother experiences a sleeping wakefulness in which they relive the bottomless woe and profound misery of their primarch's most trying time -- when he found the Emperor mortally wounded during the final hours of the Siege of Terra.
Konrad Curze Night Lords The gene-seed of the Night Lords seems surprisingly pure, bearing the least evidence of mutation. The only notable physical abnormalities were their jet black eyes and pale skin, which became even more prevalent with the introduction of the genetic material of the dour people of Nostramo. However, the real legacy of their mad primarch may have been psychological, as there was a tendency for paranoia and self-destructive behaviour displayed by many within the Night Lords. They thrive in the use of psychological warfare and fear tactics, merely for the sheer, sick joy of it.
Sanguinius Blood Angels Some Blood Angels, it is said, are driven by a terrible deathseeking madness called the Black Rage, brought on by visions of the death of their primarch. Others are afflicted by the terrible Red Thirst, a craving for blood which some claim may be the first signs of corruption by Chaos.
Ferrus Manus Iron Hands The Iron Hands possess extreme hatred for the weaknesses of the flesh which is believed to gloss over an underlying psychological fear of their physical form. As an Iron Hands Space Marine matures, that hatred and fear grows ever stronger, resulting in more extreme mechanisations of the Astartes' body. It is unclear from where this fear may originate, though many in the Adeptus Mechanicus believe that the source is a flaw in the gene-seed of the Chapter that originated some time after the death of their primarch on Istvaan V. This flaw seems to be controlled or at the very least made moot by the increasing mechanical augmentations Iron Hands Astartes undergo.
Angron World Eaters Many suspect that Angron's gene-seed was corrupt from the start and the World Eaters were damned the moment they were created. Others point to the known history of Angron and insist that his Legion could have been saved had the signs been noticed earlier. Whichever is correct, the Space Marines of the World Eaters have a physical need to shed blood and kill, a driving imperative that sends them into a berserk fury of unrestrained bloodthirsty psychosis. So strong is the desire to kill that the World Eaters will turn on one another to satisfy their bloodlust should no other foe present itself.
Roboute Guilliman Ultramarines The Ultramarines' gene-seed is by far the purest stock and there are no known aberrations in its genetic structure. Every one of the esoteric organs utilised in the arduous creation of a Space Marine by the Ultramarines are fully functional, and it can truly be said of this Chapter that they are as perfect today as they were in the days of Guilliman. As the largest Space Marine Legion, the Ultramarines contributed to the genetic repository to store gene-seed and monitor its purity. As a result, their gene-seed became the stock type for many of the Second Founding Chapters, and continued to be the most favoured stock utilised in the creation of subsequent Foundings.
Mortarion Death Guard The Legionaries of the Death Guard always reflected the gaunt, shadow-eyed quality of their primarch that gave the lie to the hardness with which they were made. The original Terran-stock displayed a stoic temperament and gene-crafted aptitude, reminiscent of their genetic inheritance from the Ironside warriors of Old Albia. With the introduction of the feral stock of pale, gaunt people of Barbarus, the Death Guard Legion's gene-seed seemed to amplify the uncommon resistance to contagion and toxins in its Barbarus recruits to unheard-of levels.
Magnus Thousand Sons This Traitor Legion's gene-seed, drawn from the Primarch Magnus the Red, was always genetically unstable and prone to rapid mutation, leading to the development of psychic powers in the majority of Thousand Sons Legionaries, but also resulting in them succumbing to a terrible mutational degeneration into what would later be recognised as a Chaos Spawn, known historically as the "Flesh-Change." Though unconfirmed, the Blood Ravens Chapter might be the Loyalist descendants of the Thousand Sons which would explain not only their unusual psychic abilities, but also their tendency to be easily corrupted by Chaos.
Horus Lupercal Sons of Horus The Sons of Horus' gene-seed, prior to the incident on Davin, was reliably pure. However, following their corruption by Chaos, Space Marines started to exhibit random mutations, and it is likely that this taint goes right down to the gene-seed level. The regular practice of seeking Daemonic possession may also have accelerated this effect. However, such mutations are seen as a mark of favour from the Chaos Gods and are generally displayed with pride.
Lorgar Aurelian Word Bearers The gene-seed of the Word Bearers was originally thought to be pure, but events subsequent to the Horus Heresy revealed the weaknesses inherent in their genetic make-up. The Space Marines of the Word Bearers displayed a marked tendency towards dogged, unquestioning belief and stubbornness that verged on insanity during the Great Crusade. Since the end of the Horus Heresy, their gene-seed has become corrupted and mutated beyond any hope of redemption by constant exposure to the energies of the Warp and the Word Bearers' original negative personality traits have been magnified to hideous proportions.
Vulkan Salamanders The strength of constitution displayed by fully developed Salamanders Astartes has measurable superiority to the already superhuman Space Marine norms in relation to extreme temperature tolerance, radiological resistance and cellular repair. These Astartes also display "ember-like" bioluminescence to their eyes and a tendency for skin pigmentation to permanently darken in response to prolonged exposure to high levels of potentially harmful radiation as part of their biological defence mechanism, often adopting an unnatural granite-like or obsidian quality with sufficient exposure.
Corvus Corax Raven Guard Since the time of the Horus Heresy, the gene-seed of the Raven Guard has suffered degeneration which has caused several of the implants to fail. Both the Betcher's Gland and Mucranoid organs are no longer functional and other defects within the gene-seed cause the skin of Raven Guard Astartes to become paler over time until it is as white as their primarch's. The eyes and hair of all Raven Guard Astartes will eventually become a deep black.
Alpharius Alpha Legion The Alpha Legion's gene-seed was surprisingly pure. The first batch of Alpha Legionaries was notably tall and strong even for members of the Astartes, physical attributes which suited Alpharius' focus on misdirection. The Space Marines of the Alpha Legion tended to pattern their visage on that of their Primarch Alpharius, an extension of the Legion's philosophy that they were a body of one that could strike in many places at once. The Alpha Legion also displayed a tendency for personal initiative and secrecy.
Second Founding Leman Russ Wolf Brothers The dangerous Canis Helix within the Space Wolves' gene-seed proved to be disastrous for this Successor Chapter, as it quickly fell to the curse of the Wulfen, and the Chapter devolved into savage, malformed lupine mutants. The Wolf Brothers were disbanded and scattered to the six points of the compass.
Rogal Dorn Excoriators The Excoriators are afflicted by a genetic curse known as Dorn's Darkness. When Dorn's Darkness takes one of their number it might appear to the untrained eye as merely a wretched palsy: a slackness of the jaw, a tremor of the limb, a blankness of the eye. But those who survive it report the experience as a living nightmare, a sleeping wakefulness in which they relive the bottomless woe of Dorn's most trying time -- the grievous loss of the Emperor during the Siege of Terra, at least as the ancient Astartes once knew Him.
Sanguinius Angels Encarmine The Angels Encarmine share many traits with their progenitor Chapter, the Blood Angels, included the tragic flaw that afflicts so many of the line of Sanguinius. This curse manifests itself in many different ways, but in the case of the Angels Encarmine it has led to a fiery, zealous temperament that drives the Chapter to ever greater heights of valour. Where other Chapters might retire after a hard fought campaign to rebuild and reconstitute their numbers, the Angels Encarmine plunge headlong into the next battle. Rarely is any time given over to recuperation, meaning that the Chapter is seldom operating at anything like full strength. It has been surmised that the Angels Encarmine fight in this manner as a means of staving off the worst effects of the flaw, but some well-placed observers have posited an alternative possibility. Perhaps, they whisper, the Angels Encarmine fight the way they do to purge their ranks of those in the grip of the Black Rage.
Sanguinius Blood Drinkers The Blood Drinkers' gene-seed, drawn from the angelic Primarch Sanguinius just like that of the Blood Angels, has further mutated, leading to a worsening of the Red Thirst Flaw in which the Blood Drinkers suffer an overriding thirst to ingest the blood of their enemies in order to stop the cravings. Unlike the Blood Angels and their other Successor Chapters, these cravings afflict the entire Chapter and not just those who fall to the Red Thirst. This has led to the development of Chapter-wide blood drinking rituals which both provided the Chapter with its name and keeps the blood-lust in check.
Sanguinius Flesh Tearers Unlike the Blood Angels and their other Successors, the Flesh Tearers are far further along in the descent into madness and their gene-seed carries a heightened version of the Black Rage Flaw which may well spell their complete annihilation within the space of a few short decades. The Flesh Tearers also suffer from the Red Thirst, an overwhelming desire to physically taste their enemies' blood. Unfortunately, when this trait is combined with the Black Rage it can devolve into outright cannibalistic assaults by the enraged Space Marines.
Corvus Corax Raptors In spite of suffering catastrophic losses multiple times throughout their history, the Raptors have managed to recover each time. This suggest that their gene-seed is healthy and stable. As with the Raven Guard, battle-brothers of the Raptors Chapter gradually attain an ever paler skin tone as they age. After just a few standard centuries of service, some have skin that is very nearly translucent. At the same time, their hair colour darkens, so that the Chapter’s Veterans are easily identified by their black hair and pale complexions. Again, like their progenitors, the Raptors also lack a functional Mucranoid implant. However, they do have a fully functional Betcher's Gland. It is unclear if this organ was somehow recovered by the Raptors or if their Founding occurred prior to the Raven Guard Chapter losing that organ from their standard array of Astartes organ implants.
Third Founding Sanguinius Flesh Eaters Born as they were from the Blood Angels' gene-seed, the Flesh Eaters also carry their flaw, although some Blood Angels' Successor Chapters feel its taint more than others. Most harshly affected are those Successor Chapters founded from the Blood Angels gene-seed in later centuries, at times when the Blood Angels Chapter Council had thought the flaw eradicated from the gene-stocks. In reality, it had merely degenerated into new and worrying forms and, as a result, the battle-brothers of those Chapters founded in such times did not suffer slight lapses of control, but teetered on the border of full-blown insanity.
13th ("Dark") Founding Corvus Corax (Suspected) Death Spectres Like the Raven Guard, the battle-brothers of this Chapter possess a minor mutation that causes the Melanochromic Organ (which controls the amount of melanin in an Astartes' skin tone) to not function properly, leading to the development of albinism in Death Spectres Astartes.
21st ("Cursed") Founding Vulkan (Suspected) Black Dragons The Black Dragons were censured by the Inquisition due to the mutation of the Chapter's gene-seed, especially the Ossmodula, which causes certain Astartes of the Chapter to develop blade-like outgrowths of bone on the head and forearms and to grow long, poisonous fangs. The Black Dragons' obvious physical mutations make long-term cooperation with other (less tolerant) Imperial Adepta impossible. The Black Dragons are a Chapter who push the Inquisition to the limits of its tolerance.
Unknown Blood Gorgons The Blood Gorgons, who value their freedom and independence above all else, were declared Renegade and Excommunicate Traitoris a mere six decades after their Founding. Even within the Eye of Terror, this Renegade Chapter refuses to swear allegiance to any patron Chaos God, preferring to serve Chaos in general in the form of Chaos Undivided.
Roboute Guilliman Fire Hawks The Astartes of the Chapter displayed a propensity for overzealousness. Several other Space Marine Chapters considered the Fire Hawks darkly tainted, overly prideful and wanting in brotherhood. Some went so far as to suggest that the Fire Hawks had been corrupted by some flaw in the Chapter's collective psyche or gene-seed, though none would gainsay their effectiveness in battle.
Unknown Flame Falcons Declared Excommunicate Traitoris within a century of their inception. Almost entirely wiped out by the Inquisition's Grey Knights after they assaulted the Flame Falcons' homeworld of Lethe, following a great victory when their bodies spontaneously burst into flames that did not burn their own flesh.
Sanguinius Lamenters The Lamenters' gene-seed may have been tampered with during their creation process by the Adeptus Mechanicus in an effort to rid them of the genetic flaws found within the Blood Angels' gene-seed. The Lamenters seem to suffer from a constant string of ill fortune.
Unknown Minotaurs Entirely consumed by a xenophobic hatred that far surpasses the righteous fury of a normal Space Marine. The Minotaurs are also prone to berserk fury and ferocious assaults. The Minotaurs have been known to show pleasure in testing their skills against worthy foes. Some speculate that perhaps the Minotaurs consider their fellow Astartes as particularly worthy, since they have a predilection for following the commands of the High Lords of Terra to castigate or annihilate a Renegade Chapter without fail or protest.
Unknown Sons of Antaeus During the inception of the Sons of Antaeus Chapter, its creators extensively modified the gene-seed in order to create Space Marines of exceptional durability, hardiness, size and strength. Whether their skeletal structure was enhanced with an artificial substance, or other more esoteric procedures were used to enhance their gene-seed is unknown. Less sympathetic observers point out that the Chapter appears every bit as resilient as the Death Guard Traitor Legion.
23rd ("Sentinel") Founding (Unconfirmed) Corvus Corax (Unconfirmed) Carcharodons The gene-seed is of unknown origin and is untainted, but has suffered some long-term degradation. More interestingly, this Chapter's gene-seed bears several genetic markers reminiscent of the Raven Guard bloodline. These markers are uncommon, and a link to the Raven Guard would explain several other details about the Carcharodons as well. The Astartes of this Chapter all possess greyish, pale skin with an almost deathlike pallor. Some of the most venerable and ancient Carcharodons have liquid black eyes, without iris or sclera. Beyond this, however, there are no common gene-types amongst encountered Carcharodons. This suggests that the Carcharodons do recruit from a wide variety of sources, and that their skin colour and eye mutation is a result of their gene-seed.
Unknown Founding Unknown Blood Ravens The Blood Ravens can no longer experience true REM sleep and so they cannot dream, and after they are implanted with their gene-seed organs, they possess perfect recall of every event for the rest of their lives. Blood Ravens Astartes also seem to develop psychic abilities at an unusually accelerated rate.

Creating Gene-Seed Implants

The gene-seed of a Space Marine Chapter is passed down through the Progenoid Glands, the 18th implant that collects and stores genetic data. There are two of these glands, one in the throat, and one in the reinforced chest cavity.

This is done mainly for safekeeping, but it also provides an opportunity for a Chapter that has suffered massive losses to regenerate itself over a long period of time.

The germ cells within a Progenoid Gland mature over a period of five to ten Terran years, and can be harvested at any time after reaching maturity, up until a short time after death. Each gland contains the seed for one of each of the specialised organs necessary to create a Space Marine.

After removal, samples are taken and cultivated to grow new organs and allow a Chapter to increase in number (although those Chapters that strictly adhere to the dictates of the Codex Astartes will generally avoid doing this because the Codex dictates that a Chapter must have only 1,000 Space Marines at maximum).

Thus, an Astartes' death means another will be added to the ranks, and the fallen hero lives on in some small way in each new warrior that follows in his footsteps using the gene-seed replicated by and harvested from his body.

In the event of a Chapter suffering disastrous losses of its gene-seed, it may become necessary for the Apothecaries of the Chapter to use test-slaves to breed enough new gene-seed to bring the Chapter rapidly back up to full strength.

These test-slaves are always Human males, usually the condemned Imperial criminals that would otherwise be turned into servitors. They are kept inside an artificial environment within the Chapter's fortress-monastery alive and partly conscious, but unable to leave their transparent plasteel gestation chamber for the full 5-10 year maturation process.

Needless to say, this solution is far from ideal, and is regarded as a last option to keep a Chapter alive. This method is also used by the Adeptus Mechanicus to create the large amount of gene-seed necessary for the Founding of a new Chapter since no existing Chapter could spare 1,000 copies of its gene-seed.

However, as each Chapter is required to tithe 5% of its gene-seed away to Mars to be checked for genetic purity, it is possible that the Imperium could build up a collection of gene-seed, and found new Chapters that way en masse.


  • Codex Adeptus Astartes - Space Marines (8th Edition), pp. 10-12
  • Codex: Black Templars (4th Edition), pg. 10
  • Index Astartes I, "Rites of Initiation - The Creation of a Space Marine" by Rick Priestley & Gav Thorpe, pp. 2-9
  • Warhammer 40,000: Compendium (2nd Edition), "The Origins of the Legiones Astartes" by Rick Priestley, pg. 7
  • White Dwarf 98 (UK) (1988) "Chapter Approved: The Origins of the Legiones Astartes" by Rick Priestley, pg. 13
  • Codex Adeptus Astartes - Space Marines (7th Edition) (Digital Edition), "The Forging of Heroes"
  • Codex Adeptus Astartes - Space Marines (8th Edition), pp. 10-11
  • Belisarius Cawl: The Great Work (Novel) by Guy Haley, Ch. 19