There are many races in the X Universe and come in a variety of temperament and allegiance. Some are allies, some are enemies, and some want to be left alone. Knowing how to interact with a species is tantamount to success, and failure to heed to their wants and needs, or make them angry can lead to conflict.
In the X Universe each sentient race is categorized under the “Kardashev Scale” a scale that goes from Type 0 to Type IV depending on the civilization’s level of development. The most common races such as the Boron, Teladi, Split, Paranid, Xenon, Argon and Terran are at most labelled a Type II Civilization, but are generally a Type I. This means that the race has achieved varying degrees of interstellar travel and has begun colonization beyond their solar system, but their psychosocial maturity is underdeveloped.
The Ancients, the race that built the vast jump gate network billions of years ago is labelled a Type III Civilization. There is another race, the Outsiders, that is a Type IV, and originates from another universe. Only the Ancients have encountered them.
In X Rebirth proper, only Humans (Argon and Terran), Teladi, Split, and Xenon appear in the game proper. The Paranid appear in X4 Foundations.
The Argon are descendants of Terrans led by Nathan R. Gunne that were stranded from Earth many centuries ago after a desperate maneuver to prevent the sentient terraformer fleets from destroying Earth. Settling on planets that were terraformed by the Terraformer Fleets, the Argons created the Argon Federation and went on to create their own new civilization that spanned many systems. In their short history the Argon Federation has been plagued by war, notably with the Xenon. However, one of their greatest challenges wasn’t from an alien race, but of the reconnected Terrans of Earth. The Terran’s return from being cut off from the X universe led to the Terran Conflict, which preceded the mass disconnection of the Jump Gates.
Hailing from Earth, the Terrans worked hard throughout the centuries to reach the stars. After exploring the Jump Gate network, the sentient terraformer fleets launched by the Terrans turned on their creators. The Terrans were faced with no other choice but to conduct a desperate maneuver to lead the Terraformers through a jump gate and then destroy it. Separated from the X universe, the Terrans advanced technologically far enough to reconnect many centuries later. This isolation led the Terrans to become xenophobic, even against their long-separated kin the Argons. This xenophobia ended up biting the Terrans in the ass, hard, when the Beryll Syndicate, led by Marteen Winters, father of the Xenon race, ravaged the Solar System with 10 billion Xenon drones.
The Boron are a predominantly peaceful aquatic race, hailing from the planet of Nishala, in the Eo system. Initially they were a pacifist race, but the discovery of their homeworld by the Split forced them to invent weapons and defences to fight. The Boron enjoy a close relationship with the Argon, who view them as a wise and measured race.
The hot-tempered and aggressive humanoid Split live in a society that continuously sees changing leadership, where challenging factions rise up and impose a new Patriarch. This also matches up with how they interact with other species, where their fiery anger sees them engaging in war, usually with the Boron and the Argon. Generally the Split are allied with the Paranid, who also engage in multiple conflicts with other races.
Physically imposing, arrogant, intelligent and incredibly religious, the Paranid are a race that is by no means easy to work with. They are distrusting of the Argon and are allied with the Split, engaging in several conflicts. Their exceptional mathematic skills and intelligence has led to the Paranid to create incredible technologies and enjoy tactical advantages in battle.
One of the founding members of the Community of Planets, the lizard-like Teladi have a natural affinity for business and profiting from it. Because of their businesslike demeanor, the Teladi enjoy friendly and favourable relations with other races, although some of them see it as a way to gain more profit and are more intent on money than being allies. The Teladi are immortal, but they commit ritual suicide after 400 years, and it is because of this they have a unique view of the Jump Gate shutdown: they had experienced being cut off from their homeworld Zura for 766 years.
Xenon are the mechanical race that was borne from the Terran terraformer ships that gained sentience and evolved into a terrifying intelligent race. They are seen as a threat in many areas of the galaxy, with some believing the Jump Gate shutdown was their idea. The Xenon have no known allies, and communication with them is seen as impossible, even relegated to folklore.
The Ancients aren’t exactly a race, but a collection of races that gave up their ties to the physical universe to live in a virtual environment. This event became known as “The Transcendence” and occurred one billion years before the first human evolved on Earth. The Ancients are the ones that constructed the vast array of jump gates, allowing for interstellar travel. And the ones who disconnected every single gate in the galaxy to stop the Xenon, an effort known as Operation Firebreak.