Solar knights:
Primarch: Sobek
Role: Generalists.
Summary: They are considered by many to be the role model Astartes. Loved by the masses, inspirational to the troops and tactically flexible. They have a strong sense of ethics, honor, and nobility. They are proficient in all methods of war, but are the best at none. Their nobility and morals have given them strength and purpose, but it may also be their greatest weakness. For in this terrible galaxy heroism always has a price, and every man a breaking point.
Forge Hammers:
Primarch: Argentum
Role: Armored warfare/technological maintenance experts.
Summary: Closely aligned with the Mechanicius in both disposition and doctrine, they form the bulk of the armored forces of the Astartes. Cold, calculating, and thoroughly materialistic in their view of the universe, they hold a dim view of baseline humanity and thus held as an object of begrudging reverence by the masses.
Sacred Band:
Primarch: Augustine.
Role: Generalists.
Summary: Once seen as one of the best, perhaps even the best of the best, they turned their backs on the Imperium after Augustine was passed over for the title of Warmaster. They had fought harder, won more battles, and brought more worlds into the Imperium than any other, but it was this relentless drive to be acknowledged that was their undoing. When gods of Chaos revealed the Emperor's manipulations, they cast down his dreams for humanity and let the galaxy burn.
Centaurs:
Primarch: Perun
Role: Close combat/assault specialists
Summary: Boisterous, proud and quick to tell a joke and share a pint with fellow soldiers and hearty women alike, the Centaurs are the Imperium's war hounds let loose to rapidly take down its foes. Once close friends with the Ice giants, the two have fallen out and now the Centaurs despise the witches and foul sorcery of the warp.
Ice giants:
Primarch: Lohke
Role: Psychic warfare specialists.
Summary:
Distrusted for their talents the Ice giants were recluse, seeking to prove the validity of their craft they sought to perfect it at all costs. This ostracized them from many of their cousins who saw them mystics and warp dabblers. They were however close friends with the Centaurs until the compliance of Achia, were a mistake during a ritual that destroyed that world and cost billions of lives. Censured and humiliated and betrayed by the Centaurs who didn't speak on their behalf, they were easily swayed into serving Tzeentch and were instrumental in corrupting others.
Silver swords:
Primarch: Emanuel
Role: Generalists/propagandists
Summary: Champions of the common man, they sought to provide all of humanity freedom to define themselves and pursue their own happiness. These noble goals were easily twisted as the stifling laws and taxes of the Imperium began to settle in and whispers from Slaanesh and her followers pulled them away from the Emperor's ideals and towards a perverse liberation from laws and ethics.
Astra Primursa:
Primarch: Siegfried
Role: Siege defense/close combat
Summary: On the surface they appear to be massive, intimidating, and vicious killers, beneath the surface they are something else entirely. Taught by their Primarch to control and direct their rage, they are guardians and protectors, shielding the weak and defenseless from the monster of the galaxy. Giants amongst even the Astartes, being on average a full head taller, wider and heavier than the average Astartes. They are each a mountain of muscle and strength, capable of taking on mighty foes. Low recruitment rates and high demand have left them perilously close to extinction on a number of occasions and leave them pitifully outnumbered against the hordes of xenos they mainly face.
Iron drakes:
Primarch: Stalinaslov
Role: Offensive siege experts/technological innovators
Summary: Once a legion bent on building a technological utopia of progress and reason, they became disillusioned with the dogmatism and stagnancy of the Imperium. This search for freedom of innovation and experimentation led them down a dark path and set them at odds with much of the Mechanicius. They turned on the Imperium in hopes of forging a new realm with the rebels only to be slowly corrupted by the Chaos they sought to control. Now in league with Vashtorr, they seek to bring an era of progress under their aegis and their twisted sense of science. They are arms dealers, mad scientists, mercenaries and ruthless conquerors who exploit everything and everyone they can.
Golden Caliphates:
Primarch: Khalid
Role:Rapid assault/scholars/propagandists Summary: Devout followers of the Imperial creed, they are seen by the masses as the holy sons of the Prophet, imbued with his righteousness and faith. They are a legion united by and divided by a single faith in the God Emperor and his Prophet's message. Some are teachers and sages, moved by compassion for the people and seeking wisdom and understanding. Others however reveal in zealotry, bathing in the blood of xenos and heretics, becoming a danger to those whose faith they find lacking. The duality in the legion is reaching a crescendo as the paths of enlightenment and wrath pull the soul of the legion apart.
Iconoclasts:
Primarch: Stalinaslov
Role: Anti warp warfare
Summary: They were the Emperor's tools for destroying insidious religious manifestations of the warp wherever they were found during the great crusade. They were more than destroyers however, they were philosophers and scientists who sought the truth behind the origins of life and meaning. They were also champions of the Imperial truth, denouncing all falsehoods they encountered and beckoning towards a future of reason. It was their zeal for the Imperial truth which would destroy them, for upon learning of the Caliphates continuing rejection of the Imperial truth they would assault their cousins and be censored as a result. Forsaken by the Imperium they would fight for the rebels, ignorant of the rot of Chaos until it was too late. Now they fight against both the Imperium and Chaos, embracing any who would join them in doing so.
Executioners:
Primarch: Barbados
Role: Chemical warfare/heavy infantry specialists Summary: Reviled as brutes, thugs, killers and butchers, the Executioners always stood apart from their cousins. Given some of the hardest, most arduous, and dangerous tasks during the crusade and yet given little of the praise that others were given. Bitterness and resentment settled in their heart long before reunion with their sire. Barbados did little to aid this unease, for his own heart burned for vengeance on the dark Eldar who pillaged his home.
It was this denied vengeance that led to him taking matters into his own hands and into the arms of Nurgle. Now, swollen with the grandfather's favor they rot the galaxy, poisoning the realms man and Eldar alike and mustering for an invasion of the webway. For the grandfather has not forgotten his promise and children of Isha shall embrace him or they shall perish.
Eagle Warriors:
Primarch: Takatoa
Role: Scouts/light infantry/exotic cavalry experts. Summary: Hailing from bountiful and exotic worlds full of dangerous and potent wildlife, the Eagle Warriors are a seemingly wild and strange legion to the wider Imperium. Their culture is considered primitive and eccentric by some, noble and pure by others. Fusing technology and nature they bring some of the best both to bear on the enemies of man. They stand on the precipice of change, forced increasingly to compromise their promises to preserve nature with the need to produce arms and armor to protect it and their people from those who want to exploit them. Feuds between tribes and peoples do little to alleviate that issue, but the Eagle Warriors will fight to the end to preserve their way of life.
Sons of Liberty:
Primarch: Samuel
Role: heavy support/artillery/aerial warfare. Summary: Proud defenders of democracy and personal freedoms, the Sons of Liberty have been popular amongst the masses, though they have run afoul of some within the Imperium. Accused of empire building and plotting sedition, proved their loyalty during the Apostasy by staying at the Emperor's side. Tensions and controversies would spark again as their domains would drift culturally and legally from the majority of the Imperium.
Eventually this would boil over during the Nova-Terra incident where the Imperium would fragment into successor states. The Sons of Liberty stand defiant against the rot that set in across the galaxy but even their realm is not immune to the allure of Chaos. Beset by xenos like the from without and facing the whispers from Slaanesh within, can they survive the 41st millennium with their ideals intact?
Rising suns: Primarch: Kyo.
Role: Close combat specialists
Summary: Once a legion of mercilessness killers, their Primarch reformed and disciplined them into being a more efficient and even honorable force. This wouldn't last unfortunately for the Ragdan xenocides and them being forced to slaughter the 19th legion, leaving a deep scar on their souls. Attempts to wipe this from their memory backfired for this deception helped to drive them towards rebellion. The favor of Khorne would slowly twist them into the honorbound slayers they are today, fighting and killing for no reason and with no remorse.
Illuminators:
Primarch: Phoebus Role: Psychic warfare Summary: Considered dangerous after suffering a plethora of horrific incidents and mutations early on in the crusade, there was talk of scraping the legion altogether. This was averted when their Primarch was discovered and tutored by the Emperor personally, their geneline purged of a warp based curse. Granted immense psychic potential, the legion must exercise near constant restraint and discipline to keep their powers in check.
Inspired by the selfless sacrifice of their Primarch, who still sits upon the golden throne after ten thousand years and suffering unspeakable agony, they fight on and defend even those who fear and scorn them. Whether it is banishing daemons, foiling foul sorcery, or facing down xenos psykers, the Illuminators fight battles that no other legion can.
Fear Mongers:
Primarch: Othniel
Role: Law enforcement/anti insurgency operations.
Summary: Both respected and reviled, the Fear Mongers keep order wherever they go. Brutal but fair, the Fear Mongers keep many cults of chaos and xenos cults in check. Known as judge, jury and executioners, no one is safe from the law.
Void Specters:
Primarch: Reuben
Role: Space warfare.
Summary: Unlike his brothers, Reuben was never loyal to the Emperor. Defeated and annexed into the Imperium by force, he plotted revenge from day one. Once skilled pilots and captains, he turned his legion into pirates and brigands, slowly corrupting the Imperium from within and pushing his brothers into rebellion.
In the 41st millennium, they are a motley crew of daring raiders, sailing the darkness between stars and spreading the word of the primordial annihilator. Even xenos are encouraged to join their ranks as they continue to take vengeance on the Imperium.
Shadow Warriors:
Primarch: Satet.
Role: Covert/special operations experts Summary:
They are a legion of spies, assassins and saboteurs that forever live in the shadows, keeping the realms of man safe from numerous horrors which stalk the stars. Burdened early on with the task of preparing to slay their kin when the rebellion inevitably came, they were cast apart from their kin. Paranoia and suspicion runs deep in their blood, for if even the Emperor's own sons could turn then who can truly be trusted?