Space Marines

Space Marines (also known as Adeptus Astartes) are genetically engineered super-soldiers who serve the Imperium of Man. They are each descended from one of the original twenty Primarchs, and are organized into chapters of 1,000 men with their own unique cultures and traditions. The Chaos Space Marines are former Space Marines who betrayed the Imperium to join Chaos.

A space marine is created via the implantation of a series of organs known as the gene-seed, derived from their Primarch. These organs make the soldier superhuman by granting them enhanced biology and extended lifespan. They are also rigorously trained for decades before joining the chapter proper. They move up the ranks as they gain experience and take up new specializations, with those who live long enough becoming veterans of the First Company, or else joining the chapter's leadership. Many chapters are differentiated by their unique traditions and heraldry, and whether or not they follow the Codex Astartes.

First Founding Chapters
The First Founding chapters have existed since the Great Crusade; all subsequent chapters are descended from one of the following chapters (though many have unknown parentage, perhaps to cover up any former ties to Traitor Legions).

A brief description of each chapter below;

Ultramarines
The Ultramarines hail from Ultramar, and are consummate perfectionists and traditionalists. They follow the Codex Astartes to the letter, and are fervently devoted to the Spiritual Liege.
 * Primarch: Roboute Guilliman
 * Notable members: Marneus Calgar, Cato Sicarius, Uriel Ventris, Illiyan Nastase

In TTS, they became an absurdly effective fighting force, having won every battle since the First Tyrannic War. They are constantly chanting every time they appear, which greatly annoys the Emperor. He has taken to calling them the "Ultrasmurfs."

Imperial Fists
The Imperial Fists are the designated defenders of Holy Terra, being masters of siegeworks and stubborn to a fault. They will endure any challenge and crush all who threaten the Throneworld.
 * Primarch: Rogal Dorn

In TTS, much like their primarch, the Imperial Fists are obsessed with constructing fortifications, including building sand castles and treehouses.

Space Corgis (Space Wolves)
The Space Wolves, or Vlka Fenryka, are a chapter of tribal warriors who fight with extreme savagery. Once known as the Emperor's Executioners, hunting down those who break their oaths to the Emperor, they have since changed to become the champions of the people.
 * Primarch: Leman Russ

In TTS, they have a fixation with naming things after wolves. The Emperor has decreed that they are to be renamed the "Space Corgis" as punishment. He also refuted Russ' claim that the Rune Priests drew their power from Fenrisian nature spirits, stating that they were in fact daemons. Their ritual for aspirant Space Wolves involves sending them into the Gate of Morkai where they will be tempted by the Chaos Gods; any unworthy aspirants are killed if they "pop a boner," especially if it involves anything wolf related.

Dark Angels
A chapter of secretive hooded monk-knights, the Dark Angels have their own unique structure that emphasizes hard-hitting weaponry and heavy armor in combination with a large cavalry force. They are obsessed with keeping the existence of the Fallen Angels secret, and will ruthlessly hunt them down.
 * Primarch: Lion El'Jonson
 * Notable members: Azrael, Asmodai, Belial, Snurko

In TTS, the Dark Angels are extremely twitchy and paranoid, especially the Inner Circle.

Salamanders
The Salamanders are extremely hardy and resistant to fire, with flamers being one of their favorite weapons. Despite this and their intimidating appearance, they are among the most humane space marines, and always put the welfare of mortal humans above their own.
 * Primarch: Vulkan
 * Notable members: He'Stan, Tu'Shan

In TTS, the Salamanders are extremely oblivious and are most likely very deaf, being unable to hear very loud noises behind them. And despite Vulkan's obvious regenerative powers as a Perpetual, the Salamanders will always mourn his death and celebrate his return, sometimes in the span of less than a minute. The Salamanders' blacksmithing prowess was demonstrated when He'Stan and Tu'Shan were able to craft 5,000 perfect Death Masks of Vulkan in only 24 hours, in an effort to pay off their debts to Jopall.

Blood Angels

 * Primarch: Sanguinius
 * Notable members: The Sanguinor

The Blood Angels live a dualistic existence. On the one hand, they are a noble chapter, who seek to better the Imperium before any personal glory. On the other hand, they are cursed with the Red Thirst, which drives them to consume the blood of foes, and the Black Rage, an incurable madness that manifests over time in all members. These curses keeps them humble as they dutifully carry on the legacy of their Primarch.

In TTS, the Blood Angels cry non-stop during Sanguinala every year to mourn the loss of their Primarch.

White Scars
The White Scars are nomadic tribesmen who specialize in cavalry and shamanism. Despite their loyalty and actually cultured side, they are sometimes viewed as outcasts for their nominally savage nature and solitary existence.
 * Primarch: Jaghatai Khan

The White Scars are the subject of the pilot episode of If The Emperor Had a Podcast. They are described as being obsessed with going fast (the phrase "ULTRA-RAPID DEPLOYMENTS" is used repeatedly) and have a "Head Chaplain" whose sole responsibility is to preserve the heads of his chapter's enemies. The Emperor finds them boring and ineffeicient, but nonetheless effective in their role as shocktroops and hunter-killers.

Iron Hands
The Iron Hands follow the religion of the Adeptus Mechanicus, and routinely augment themselves to the point of emotional inhibition, believing that the Flesh is Weak.
 * Primarch: Ferrus Manus

Raven Guard
The Raven Guard specialize in ambush tactics and surgical strikes. Every company is a self-sufficient unit that can coordinate devastating attacks at their enemy's weakest points using a minimal number of men.
 * Primarch: Corvus Corax
 * Notable members: Kayvaan Shrike, Kadus

In TTS, the Raven Guard are very self-deprecating, but also eager to come to the aid of others. They frequently make cawing sounds when distressed.

Black Templars
The Black Templars keep the spirit of the Great Crusade alive, maintaining massive crusader fleets that are constantly fighting and recruiting from the worlds they liberate. They reject most organizational conventions and assault with savage fury, with particular emphasis on purging mutants, psykers, and heretics.
 * Successor of: Imperial Fists
 * Notable members: Chaplain Grimaldus, Helbrecht

In TTS, Rogal Dorn refers to them as insane maniacs, and he wants very little to do with them. The Black Templars are the subject of Podcast Episode 2: The Black Templars. The Emperor attempts to teach them how to control their anger and to not cause collateral damage to otherwise loyal members of the Imperium by forcing them to accept psykers, ratlings, and "people who are too vocal about their opinions" in their ranks.

Grey Knights
The Grey Knights are a specialized and secret chapter made for the sole purpose of hunting Daemons. As such, they are heavily trained to resist chaotic corruption and how to identify the weaknesses of their enemies. They are all psykers and use force weapons to enhance their combat effectiveness. The Grey Knights work with the Inquisition's Ordo Malleus, usually deploying in response to major daemonic incursions, especially if any of the Daemon Primarchs appear.
 * Created by Malcador the Sigilate
 * Notable members: Kaldor Draigo

In TTS, the Grey Knights have an obsession with covering themselves in Sororitas blood due to an incident in the official lore where they used the blood to protect themselves from the Bloodtide. This story is widely mocked for being completely unnecessary and excessively violent for the Grey Knights.

Deathwatch
The Deathwatch is an organization made up of brothers from all Astartes chapters. They are selected for their proficiency at killing xenos, and are organized into small kill teams to eliminate threats that larger forces cannot destroy so easily. The Deathwatch works closely with the Inquisition's Ordo Xenos in eliminating alien threats.
 * Recruits from all chapters
 * Notable members: Calato, Wilford

The Deathwatch feature more prominently in the BEHEMOTH Trilogy as they discover and respond to the arrival of the Tyranids into the galaxy.

Astral Knights
The Astral Knights were known primarily for taking down the Necron weapon known as the World Engine, though they became extinct in the process.

In TTS, the Emperor showed little interest in them as he had never heard of them before. Upon learning of their heroism in taking down the World Engine, he joked that they were a super special secret legion created before the Great Crusade, and that "they were the best around, nothing was going to keep them down."

Blood Ravens
A chapter that features prominently in the Dawn of War games. They have an obsession with knowledge and collecting artifacts, with a common meme being that they have outright kleptomania.
 * Unknown Primarch (suspected to be Magnus the Red)
 * Notable members: Indrick Boreale, Apollo Diomedes

In TTS, Kitten mentioned them when the Emperor was looking for someone to steal from Trazyn the Infinite, though they were interrupted before going into detail. The Blood Ravens may or may not be descendants of the Thousand Sons. The Blood Ravens feature more prominently in BEHEMOTH as an auxiliary force assisting Kryptman and the Deathwatch. The Blood Ravens are also considered the "Spiritual Lieges" of the Alfa Legion, as the many memes they spawned had been readily embraced by its members. So far they’ve had very short cameos, but currently captains Diomedes and Boreale are in the custody of Magnus the Red.

Marines Malevolent
A chapter that cares nothing for civilians or collateral damage. They nearly came to blows with the Salamanders on Armageddon when they bombed a refugee camp to get at the Orks.

In TTS, the Emperor, disgusted with their actions, ordered for virus bombs to be dropped on them. He claims that their bad attitude is a result of a gene-seed mutation that causes sharp protrusions to grind against the walls of their rectums.

Flesh Eaters
The Flesh Eaters have a hyperactive Omophagea gland, allowing them to see the memories of their foes by consuming their flesh, gaining much insight into the enemy.
 * Successor of: Blood Angels

In TTS, the Flesh Eaters came about when a Blood Angels squad received a vision of Sanguinius telling them that he hungered for “HERETIC BURGER” After consuming Ork flesh.