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"They shall be my finest warriors, these men who give of themselves to me. Like clay I shall mould them and in the furnace of war I shall forge them. They shall be of iron will and steely sinew. In great armour I shall clad them and with the mightiest weapons shall they be armed. They will be untouched by plague or disease; no sickness shall blight them. They shall have such tactics, strategies and machines that no foe will best them in battle. They are my bulwark against the Terror. They are the Defenders of Humanity. They are my Space Marines...and they shall know no fear."
—The Emperor of Mankind
Gene-Seed Implant 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 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 Space Marine. All of the gene-seed was originally crafted in the 30th Millennium by the Emperor of Mankind in his secret gene-laboratories located 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.


The stages of a Neophyte's transformation into a fully-fledged Astartes.

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 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 was never a set way to activate these transformative functions of the gene-seed.

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

Great Crusade & ExpansionEdit

As the Great Crusade continued the expansion of the nascent Imperium into the galaxy, the discovery of the Primarchs and their newly adopted homeworlds helped to stem an impending crisis that was not widely known of at the time outside of the exalted ranks of the Imperium's ruling War Council: namely, the diminishing stability of the gene-seed itself through over-use and the increasing need for ever greater numbers of Space Marines in the field. This was a matter that only worsened as the Great Crusade pushed ever wider afield into the galaxy. Imperial forces could no longer be concentrated as easily as before, and attrition was taking its toll as years of near-constant battle became decades. To relent the pace of the Great Crusade's progress was for the Emperor simply not an option and so the simple truth was that more Space Marines were needed and they needed to be created faster than before.

A secret conclave of gene-wrights under the Emperor's direct supervision posited the solution that became known as Grabiya's Theorem, which demonstrated that a Primarch's genetic code could be used to stabilise and expand Astartes gene-seed stocks with what was hoped to be "minimal deviation." Alongside this accelerated gene-culturing technique, other previously unavailable genetic technologies were put into effect, reducing the processing time required to create a battle-worthy Space Marine to a single Terran year in some cases. Such accelerated gene-seed techniques, along with absent, inadequate or over-forceful psycho-doctrination techniques, were later found to have unseen fundamental flaws. Many Imperial savants since have come to believe that the drive to create larger Space Marine Legions at accelerated speed played a prime role in the degradation of the sanity and psychological make-up of certain Legions and paved the way for the horror that was to come.

Known Gene Seed MutationsEdit

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 a couple centuries since the Space Marine Legions were first created, a Space Marine Legion's gene-seed can mutate, producing new and hitherto-unknown physiological effects in that Legion's Space Marines or simply becoming non-functional. Repeated exposures to the corrupting energies of Chaos can also cause mutation within the gene-seed.

Legion Name
Genetic Idiosyncrasies/Mutations
Celestial Legion
Ankhaya Vhadarsha
Ascetic Transcendence - Not only as part of their training, the Celestials are unfazed before most terrors, slaughters and other nerve wracking situations. Furthermore, elder and veteran legionnaires often develop a unique focus on an aspect of warfare, making them extremely proficient at their chosen facet of warfare - but to the exclusivity of all else. These doctrines are so internalized, that they cannot be passed down - which is why, while there are several legendary warriors, they cannot transmit their experiences, if not through cryptic and prophetic teachings.
Sanctified Sons
(To be added)
Crescent Moons
(To be added)
Gryphon Knights
Lordin Tolken
(To be added)
Omni Legion
Vilhelm Dotharl
(To be added)
Argonite Reavers
Valerian Sygarian
(To be added)
Sollis Immortals
Cyrus Khosrow
(To be added)
Gladius Voss
Obsessiveness - Upon initial review of the VII Legion, it was determined later on during the Great Crusade that certain Imperators tended to develop a psychological flaw that emitted from a near-concentrated need for glory and combat expertise. As the Great Crusade continued, more Imperators began to behave differently and certain situations arose that compromised the Legion's command structure by more daring and ambitious Legiones Astartes competing with each other for more power within the legion.
Jade Legion

Soulthirst - The Jade Legion recruits solely amongst the population of psychic mutants, as normal humans introduced to their gene-seed often ends up being consumed by the augmentations meant to strengthen them. However, when a psyker successfully becomes implanted with the gene-seed the ability to feed on the immaterial presence and soul of those around them becomes an ability - almost a necessity. It is not unheard of for the Jade Legion to utilise this inherent ability to subdue wayward planets, consuming the very souls of the rebels that would deny the authority of the Imperium or the Legion. As a result of their vampiric powers, both active and passive, daemons of the Warp tend to stay away from a psyker at the peak of their might, otherwise they might just be consumed as sustenance for the sorcerer's æthereal being.

Dragon Lords
Draconic Breath - A mutation within the Dragon Lords' Betcher's Gland makes it split into two facets - one, which produces a flammable liquid which can be spurted out of a legionary's mouth, which can then be ignited by the other half of the gland, which produces a modified acid which then sets the liquid alight. In effect, allowing the legionary to literally spit fire like a dragon. Hence, the name 'Draconic Breath'. They also maintain the usual ability of the Betcher's Gland to produce highly corrosive acid.
Argent Hand
The Argent Son
(To be added)
Xenophon of Atina
(To be added)
Cobalt Paladins
Ralech Gwynson
(To be added)
Emperor's Dragons
Theodore Pendragon
Crimson Hands
(To be added)
Sons of the Morningstar
Lucius Aurelius
(To be added)
Grave Lords
Dargus Mortane

Overzealous Retribution - The Grave Lords display a propensity for the use of violence and calculated, cold-blooded murder in order to achieve their aims. They have a keen understanding of the human psyche, and willingly employ such brutal tactics in order to maintain Imperial order. When committing such horrible acts, they often display cold indifference when enacting their brutal forms of justice - as cold and uncaring as their ritual flaying knives. Though deemed barbaric and bellicose in nature by many of their fellow Legiones Astartes, the Grave Lords are known to display unequivocal loyalty to the tenet, if not the letter, of enacting the Emperor's will against recalcitrant worlds.

Call of the Grave - Often, certain battle-brothers will display suicidal urges and a blatant disregard for overall combat doctrine. Gathered together in specialised units known as 'Death Seekers', these battle-brothers operate independently on the field of battle, and are often employed as efficient shock assault troops and assassins. Primarch Mortane will often utilise such afflicted brethren to undertake suicidal Zone Mortalis missions from which they are not expected to return. These battle-brothers will undertake such missions willingly, to rid themselves of the dark visions that plague their every waking moment, and to sell their lives dearly in service to their gene-sire.

Honour Bound
Increased Muscularity & Lack of Pain - During the Founding of the Honour Bound Legion, the Magos Biologis fleshcrafters of the Mechanicum extensively modified their gene-seed in order to create Space Marine Legionaries of formidable strength and exceptional durability and toughness. Legionaries of the XIX Legion are noted for being particular robust specimens, possessing exceptional strength of constitution which has measurable superiority to the already superhuman Space Marine norms. It is believed by Imperial savants that the Biscopea implanet, known as the Forge of Strength, was genetically modified so that it would produce increased muscularity and survivability to superhuman levels, enabling these legionaries to fight on despite suffering horrendous wounds, severed limbs and massive trauma that would normal fell even an Astartes. Despite the benefits of their gene-seed, there are also a number of inherent flaws that began to manifest soon after their inception. Most notably is that with the increase in muscle mass, the over-active Biscopea also produces increased production of adrenaline, resulting in greater strength and aggression in battle. While in battle, the production of the neurotransmitter serotonin in the legionary's brain encourages instinctive aggression and deadens all other forms of emotional response and neuroelectrical activity to all parts of the brain save for that which regulates the flow of adrenaline. Over time, the affected Legionary's thirst for blood of their foes becomes almost uncontrollable between battles. Near the end, those who are most affected by the rapid deterioration caused by their gene-seed's flaw, become little more than an animal filled with fury and madness, striking out at all those around them.
Earth Breakers
Castor Magni
(To be added)