The Adeptus Astartes, also known as the Space Marines, were a military force of the Imperium of Man in a possible far future. By the 41st Millennium, they were divided into numerous autonomous armies known as chapters.
Space Marines were genetically enhanced supersoldiers. Their creation involved genetically modifying ordinary Humans at a young age. However, Human is a much broader term in the Imperium. These modifications made the subjects an advanced type of Augment. However, there were traces of Klingon DNA in all Space Marines; it is possible that the Klingon brak'lul organ redundancy was duplicated in the Space Marines using these genes.
Chapters also included Techmarines, battle-brothers who were members of the Cult Mechanicus and so provided technical, mechanical, and engineering experise.
The battle-brothers also had help from Chapter Serfs, ordinary people who carried out various tasks. These included artificers (who look after armour) and starship crew.
There were also several Space Marines who had turned to Chaos, the archenemy of the Imperium. These Chaos Space Marines are frequently mutated and often enlist the aid of Daemons. With the aid of splinters of their gods, Chaos Space Marines can be a formidable force. However, many have equipment that is 10000 years out of date.
The Space Marine chapters known as the Blood Ravens and the Space Wolves provided assistance to the USS Enterprise (NCC-1701) after it appeared in the far future. The Enterprise had been duplicated so well that it was impossible to tell which ship was the original and which the duplicate, and one ship was pulled into the future. It emerged that an alien race known as the Eldar (possibly descendants of the Romulans) had summoned the Enterprise so the crew could restore the USS Miranda and Enterprise (NX-01). Both ships were reduced to derelicts stuck in a Space Hulk, a giant collection of stellar debris often used as a base by Chaos Space Marines. The Eldar believed that Chaos should not be allowed to take the vessels for themselves.
Chapters
Black Templars
This chapter was known for its fanaticism; it was on a permanent crusade against the Imperium's enemies. The Black Templars' leader is the High Marshal, who at the time of the Enterprise's visit was a Betazoid.
Blood Angels
This chapter is genetically flawed and susceptible to uncontrollable rage. To compensate for this, it focus on flawless standards and drill. Some Space Marines are Vulcans with no emotional control.
Blood Ravens
This chapter focuses on gathering information and studying its enemies. This proved vital as it meant the Blood Ravens had the specifications of the Constitution class on file. The Blood Ravens strike cruiser Bibliothèque took the Enterprise to the Reolaz star system for repairs but then had to rescue the crew after a rogue faction of the Adeptus Mechanicus destroyed it. Blood Raven battle-brothers then aided the surviving crew in their effort to restore the derelict ships and defeat the Chaos Space Marines. The Blood Ravens who aided the Enterprise include Captain Gabriel Angelos of the 3rd Company, Master Apothecary Steve, and Sergeant Tulka. Several battle-brothers of the 3rd Company were Bolian, including Tulka. The chapter serfs of the 3rd Company included Artificer Gana (an Orion), Optio Suma (a Vulcan), Centurion Ro Edon (a Bajoran), and starship Captain Ufrat (a Human).
Death Guard
This Chaos Space Marines served Nurgle, the God of Decay. They had a substantial number of Plague Marines, diseased supersoldiers who were remarkably tough because they had so many infections. A group of Death Guard were on the Space Hulk containing the derelict starships.
Knights of the Silver Tower
This Chaos Space Marine warband served Tzeentch, the God of Change. They had turned traitor only seven years before the Enterprise's visit, making them a relatively new group. Unlike some Tzeentchian Astartes, the Knights were still alive, not the haunted armour known as Rubric Marines. Some Knights attempted to seize the Miranda and Enterprise aboard the Space Hulk. One of their Sorcerers mutilated Lieutenant Arla and killed Yeoman Landon.
Screaming Skulls
This Chaos Space Marine warband served Nurgle. They also wanted the starships inside the Space Hulk. One of their Sorcerers killed Lieutenants Sulu and Uhura aboard Enterprise.
Space Wolves
This chapter was known for its feral, wolflike behaviour, but also for being one of the more benevolent chapters. Their religious, supernatural, and medical needs were handled by Wolf Priests whilst Iron Priests dealt with technical matters. One of its ships, Firemane's Fang, helped the Blood Ravens defend the Enterprise during the Mechanicus attack before picking up some escape pods. Another group aided the Rogue Trader starship Voyager board the Space Hulk before joining the Firemane's Fang task force and aiding the Starfleet crew. Some Space Wolves were Klingon. The Space Wolves included Wolf Lord Kiod (a Human) and Blood Claw Faru.
Thousand Sons
This Chaos Space Marine warband served Tzeentch. It was made up of Rubric Marines, Space Marines who had been exposed to the Rubric of Ahriman. This destroyed their bodies and left them as spirits trapped inside armour. They typically did not speak and were led by Sorcerers. A group of Rubric Marines were on the Space Hulk that contained the derelict starships.