6. Warhammer 40k factions Xenos alien species
Other alien species in the Galaxy, such as the Eldar, were once the most powerful empire in the Galaxy before the rise of the Imperium. They are a long-lived and extremely psychic species, but their power and hubris saw their home worlds consumed by chaos. In the universe of Warhammer 40,000, they are a dwindling, dying race living in fear of their souls being eaten by the warp. They try to avoid this fate by living on vast wraith-bone spaceships known as craft worlds.
Craft worlds are gigantic cities that float through space, leading ordered and contemplative lives. They dedicate themselves to different structured paths in order to stave off the warp. Their forces are made up of various warrior aspects of their ancient dead gods and wraith-bone constructs powered by Eldar souls trapped within Spirit Stones. They are led by Farseers who manipulate the strands of Fate to ensure the Eldar's survival. On the other hand, the Drakari are cruel and sadistic Eldari pirates who live in the Webway, halfway between real space and the warp. They have no access to Spirit Stones and replenish their ever-fading souls by torturing prisoners taken in raids. Their society is split between the cabals that rule their dark city of Kimora, the gladiatorial Witch Cults, and the Homunculus covens who guarantee unnaturally long lives to the rest of the Drakari by performing hideous experiments on enslaved species. In between these two main factions are the Harlequins, deadly dancers and performers who travel between both factions' societies to keep the old Eldar myths alive, and whose souls are pledged to their laughing god, Kegerak. The Ynnari, a cult of the Eldar god of death, and other factions like the Pirate Corsairs or the Exodites, who retreated from the fall of the Eldar to the most verdant and far-flung planets in the ancient empire, are also present in K.
All the Eldari were originally created by the long dead and near-mythical race known as the Old Ones. The Kin of the Leagues of Voltan are not officially part of the Imperium and are descended from the earliest human colonists who settled near the Galactic Center. They have preserved much of the Lost technical knowledge of humanity in the form of huge data cores known as Votan. By the time of K, the Kin of the Leagues are genetically engineered clones created by the Voltan and genetically tailored to whatever job is needed. Their armies reign across the galaxy, identifying planets that might be ripe for exploitation and profit. They are stocky, serious, and durable, and yet they are fantasy dwarves in space.
K also has Orcs. Like the Eldari, the Orcs were created long ago by the Old Ones for one thing only - war. But after millions of years, they have forgotten their origins and are now a dangerously random problem for everyone else in the galaxy, rampaging around in colossal migrations known as Waaaghs! They are kind of the comic relief in K, and their society is based entirely around fighting. They go to war in ramshackle vehicles accompanied by a range of squiggly beasts to ride, fight, eat, wear or attack with. They also speak like football hooligans, for some reason - it's a common orc thing.
The Tau Empire is a small self-contained civilization in the galactic east and the sort of xenos threat that the Imperium would probably have wiped out earlier if they weren't beset on all sides by more pressing matters. The Tau are an optimistic and hopeful faction divided into five elemental casts who work to advance their philosophy of the Greater Good. They fight from within high-tech Battle Suits or advanced vehicles and are supported by a range of alien species they've absorbed into their growing empire.
The Necrons are the oldest race.
They fought a great war against the Old Ones millions of years ago, which prompted the creation of many other species to fight for them. After half of the galaxy was destroyed, the Necrons went to sleep, with their ancient dynasties surviving in skeletal metal bodies on great tomb worlds. As the first millennium comes to a close, they are beginning to awaken. The Necrons are comparable to space undead, leading legions of durable automatons, overseen by cunning overlords and Crypteks whose advanced science appears magical to others.
Next up is the ultimate end, the Tyranids or the Great Devourer. The Tyranids are a swarm of extragalactic bugs that are drawn to the light of our galaxy and exist solely to consume. They land on planets, strip them clean of biomass, and leave behind only barren, lifeless rocks. As the swarm progresses, they are entirely alien and inscrutable, utilizing a technology that is entirely biological and governed by both animalistic instincts and the hive mind's collective intelligence. However, they are capable of planning, as shown by their Genestealer offshoot faction. The Genestealers are Tyranid bioforms created to infiltrate unsuspecting worlds, propagating through the population like a parasite and controlling their followers with a low-level psychic field. Genestealers destabilize the host planet from within, leading to a bloody revolution just as the higher fleet of Tyranids approaches, accelerating the planet's demise.