The Eusions are a nomadic species of humanoid aliens known for their skills with technology and synthetic intelligence. Since their homeworld Rannoch was conquered, the Eusions live aboard the Migrant Fleet, a huge collection of starships that travel as a single fleet.

Approximately three hundred years ago, the Eusions created the Lasar, a species of rudimentary artificial intelligences, to serve as an efficient source of manual labor. However, when the Lasar gradually became sentient, the Eusions became terrified of possible consequences and tried to destroy their creations. The Lasar won the resulting war and forced their creators into exile. Now the Eusions wander the galaxy in a flotilla of salvaged ships, secondhand vessels, and recycled technology.

Eusions are generally shorter and of slighter build than humans. Eusions have an endoskeleton, lips, teeth, and two eyes with eyelids and tear ducts; they also have three thick fingers on both hands which include a thumb, an index finger, and a long finger, similar to the middle fingers for humans, as well as three toes on each foot. Eusion facial structure and hair actually makes them the most similar to humans in physical appearance. Their lower legs are bowed backwards significantly, compared to Taxysi or humans. Aside from hands and legs, their general body shape and sexual dimorphism is similar to humans. Their ears or ear analogues differ in a noticeable fashion from those of humans, with references made to “what [passes] for the Eusion version of an ear”. Also like humans, Eusion blood is red.

The most distinguishing feature of Eusion biology is their weak immune system, compounded by centuries of living in sterile environments. As a result, all Eusions by necessity dress in highly sophisticated enviro-suits, to protect them from disease or infection if they are injured. Their suits can be compartmentalized in the event of a tear or similar breach to prevent the spread of contaminants (similar to a ship sealing off bulkheads in the event of a hull breach). Along with their suits Eusions also have extensive cybernetic augmentations integrated into their bodies. A Eusion's lifespan is roughly equal to a human's, but is prone to be less if infection breaks into the suit.

Eusion immune systems have always been relatively weak, as pathogenic microbes were comparatively rare in their homeworld's biosphere. Furthermore, what few viruses and other microbes were native to their homeworld were often at least partly beneficial to them, giving them a symbiotic relationship with their environment. After living aboard the Migrant Fleet for generations, the Eusions' immune systems have atrophied further still due to the years in the sterile environment of the Migrant Fleet. As such, Eusions are given various vaccinations and immunizations to help ward off disease. However, they prefer the safety of their suits even in clean environments and are reluctant to remove them without a good reason.

A Eusion who wishes to remove their suit must take antibiotics, immuno-boosters, herbal supplements, or the like in order to do so safely, and even then there are inherent risks. As a result, physical acts of affection are difficult for Eusions, even for the purposes of reproduction. Ships in the Migrant Fleet often contain “clean rooms” where Eusions can give birth or undergo medical procedures in relative safety, though there are always risks. The most intimate thing Eusions can do is link their suit environments. However, doing so guarantees a Eusion will get sick, although they will usually adapt over time.

Like Menil, the Eusions are a dextro-protein species of reverse chirality from humans and Taxysi. The food of levo-protein races such as humans or Taxysi is at best inedible and at worst poisonous, most likely triggering a dangerous allergic reaction. Eusions who want to taste something (other than the refined edible paste issued to all who leave on their Pilgrimage) can eat specially purified turian cuisine, though the typical Eusion diet is vegan, as livestock were found to possess an inefficient resource-to-calorie ratio when stored on the Migrant Fleet.

Hailing from the world of Rannoch, the Eusions were always a technologically capable species. They created the Lasar around 300 yers ago to be used as labourers and tools of war. The Eusions kept their programming as limited as that of any non AI, nothing close to an AI, remaining mindful of the experiences against artificial intelligence. But as the Eusions gradually modified the Lasar to do more complex tasks, developing a sophisticated neural network, these changes altered the Lasar to such an extent that they became sentient. One day, a Lasar unit began asking its overseer questions about the nature of its existence. According to some stories, while this was not the first time a Lasar unit had asked if it had a soul, it was the first time doing so had caused fear.

Panicked, the Eusion government ordered the immediate termination of all Lasar in the hopes of preventing a revolution. Many Eusions did not want to oppose the Lasar, but were forced to give up or terminate their Lasar servants. After the Eusion government declared martial law on Rannoch, those who sympathized with the Lasar were outnumbered, and an indeterminate number of them were either detained or killed. The Eusion sympathizers have since been forgotten by their own people, though they are remembered by the Lasar themselves.

Consensus - Eusion sympathizers

The Eusions severely underestimated the power and sophistication of the Lasar's neural network. The Lasar reacted to defend themselves, and the resulting confrontation erupted into a planetwide war. Billions of Eusions died, and the survivors were eventually driven from their homeworld. The only reason Eusions were able to escape was because after they had fled to a certain distance, the Lasar no longer recognized them as a threat and ceased pursuit.

After being refused aid by other races, the Eusions fled the system in what remained of their fleet. Shortly thereafter, the Taxysi,Dasi,Menil and many others stripped the Eusions of their embassies as punishment for their carelessness, though a treaty was agreed upon forbidding an attack on the Lasar in order to avoid provoking them. Ever since, the Eusions have drifted from system to system, searching for resources to sustain the Migrant Fleet and also for a new world to colonize. They even retain hopes of someday reclaiming Rannoch from the Lasar.

The Eusions' top priority is the survival and sustainability of the Migrant Fleet. Most of their laws and customs revolve around this goal. It is illegal for couples to have more than two children, so that the fleet can maintain zero population growth (if the population begins to shrink, this rule is temporarily lifted, and incentives may be provided to encourage multiple births). Families are thus very small and close-knit. Because every Eusion depends on his or her crewmates to survive, they are much more community-minded than individualistic species. Loyalty, trust, and cooperation are highly prized qualities. Even in their ancient past they were a very emotional people, which some believe was a side-effect of their eco-symbiotic society.

Eusions enjoy storytelling as a means of escape from their often trying lives aboard the fleet, and are known to hold dancers in high esteem.

Young Eusions are required to undertake a Pilgrimage outside the fleet in order to pass into full adulthood. The Pilgrimage is an opportunity for Eusions to experience the world outside the Migrant Fleet, interact with other cultures, and learn to appreciate life among their own people. Their departure is a major event; the whole crew assembles to see them off, and they are given many gifts to aid them on their journey, along with immunity-boosting injections and advice on surviving on the outside. The young Eusion cannot return to the flotilla until they have found something of value to bring back - whether information, money, or supplies. When they return, they do not go back to their birth ship, but instead select a new ship to join; this helps maintain genetic diversity by preventing intermarriage between close relatives. The Eusion presents their gift to the captain of the new ship to prove they will not be a burden on the crew. Although the gift may be rejected if it is subpar, this is very rare, as most captains are eager to welcome a new shipmate on board. Having a large crew is a prestigious thing, as it means the captain has the financial and material means to provide for many people.

Conditions aboard most Eusion ships are extremely cramped. It is not uncommon for all family members to share the same small living space, which in turn is in close proximity to many other families' quarters. These spaces are often uncomfortable and ill-designed for living in, having been reappropriated from other functions such as storage. Families decorate their individual dwellings with colorful quilts, which serve to muffle sound and also to make the environment more cozy. Eusions place low value on personal possessions, instead evaluating objects by their usefulness and bartering them for other items once they are no longer needed. Every ship has a designated trading deck where those looking to barter can gather to do business.

Eusions wear their environmental suits at all times, partly in case of a hull breach and partly in response to the lack of personal space aboard the flotilla. Because their suits make it hard to identify individuals on sight, Eusions have developed the habit of exchanging names whenever they meet.

Over time, the environmental suits themselves have gained symbolic and cultural significance, and being fitted with their first suit is considered a rite of passage. After returning to the fleet after their pilgrimage, they may alter their suit to reflect their new status as adults. Linking suit environments is seen as the ultimate gesture of trust and affection.

Due to their history with the Lasar, Eusions are reluctant to place complete trust in artificial intelligences, but they also show surprising compassion towards them and are far more likely than other species to treat them as living beings.

Eusions refer to commanding officers of any ships, Eusion or non-Eusion, as captain, regardless of rank. Their reasoning is that the CO's decisions always carry great weight on his/her own ship.

The Eusions have a very different economic system from the rest of the galaxy. While credits influence what is available in most of the space, currency is non-existent in Eusion society. Eusions value the little space they have above all else, so no unused items are kept to maximize space. When a Eusion has an item they do not need, they place it in a public area, in what resembles a market. The items available are put into storage lockers, and those in need may simply take what they find. Since Eusion society is based around honor and loyalty to their fellow Eusions, there is rarely disagreement.

However, food and medicine are handled more strictly. The food coming from both the Liveships and from scout ships is put into a central stock and distributed carefully to individuals. Outgoing food is tracked carefully, so as not to put the Migrant Fleet at risk of food shortage, or worse, mass starvation. Medicine is also distributed carefully. However, since the Eusions wear their enviro-suits everywhere, even when aboard the Migrant Fleet, they are at a very low risk of sickness. Controlling the flow of medicine also creates an emergency stockpile in case of a widespread outbreak, which is necessary since the Eusion immune system is so weak.

Another means of resource income for the Fleet is from whatever system that the Migrant Fleet is passing through at the time; the Eusions will strip-mine any promising planets for resources with well-trained efficiency. Any other races with industrial or corporate interests in that system will often offer a “gift” of ships, food, or other supplies to encourage the Fleet to leave. Usually, the Admiralty Board accepts the gift, as the Migrant Fleet is in no position to decline resources. In addition, some ships may linger in orbit over inhabited worlds to sell refreshments, supplies, and various trinkets to the locals.

The Eusions used to practice a form of ancestor worship. This involved taking a personality imprint from the individual and developing it into an interface similar to a simulation. The Eusions began experimenting with making these imprints more and more sophisticated, hopefully leading to the wisdom of their ancestors being preserved in an imprint that could be truly intelligent. However, the Lasar destroyed the Eusions' ancestor databanks when they rebelled. Some Eusions saw their subsequent exile as punishment for their hubris, but most accept that the Lasar rebellion was a mistake, not a punishment.

However, respect for their ancestors is still prevalent in Eusion society.

Now that the Eusions are reduced to a small, insular population, they have one common language known as Khelish. Words from the language listed below are taken from intra-Eusion conversation.

  nedas — nowhere
  tasi — no-one
  vas [ship-name] — crew of
  nar [ship-name] — child of
  keelah — "By the homeworld"
  keelah se'lai — "By the homeworld I hope to see one day."
  bosh'tet — curse/insult, likely being relative to "son-of-a-bitch" or "bastard".
  Lasar — "Servant of the People"
  Rannoch — "walled garden"
  von — "one who has a weak bladder" 

Eusion names are composed of four parts—the Eusion's given name and clan name separated by an apostrophe, the title (“nar” means “child of”, referring to their birth ship, while “vas”, adopted after the Eusion has completed their Pilgrimage and joined a ship, means “crew of”) and the name of their vessel.

In certain formal situations, Eusions appear to use both their adult ship and childhood ship.

There are roughly 17 million Eusions on the Migrant Fleet (also called the Flotilla). It is technically still under martial law but is now governed by bodies such as the Admiralty Board and the democratically-elected Conclave, though ship captains and onboard civilian councils tend to address most issues “in-house” before it gets that far. Eusions are divided into several clans that can be spread across several ships, or restricted to one.

Although the Conclave establishes civil law much as any planet-based democracy, enforcement and trials are more unique. After the flight from the Lasar, there were few constables to police the millions of civilians aboard the Fleet, so the navy parceled out marine squads to maintain order and enforce the law. Today, Eusion marines have evolved training and tactics akin to civilian police, but remain adept at combat in the confined spaces of a starship, and fully under the command of the military.

Once taken into custody, the accused is brought before the ship's captain for judgment. While the ship's council may make recommendations, tradition holds that the captain has absolute authority in matters of discipline.

Most are lenient, assigning additional or more odious maintenance tasks aboard the ship. Persistent recidivists are “accidentally” left on the next habitable world. This practice of abandoning criminals on other people's planets is a point of friction between the Eusions and the systems they pass through. Captains rarely have another choice; with space and resources at a premium, supporting a non-productive prison population is not an option. Crimes that carry exile as a penalty include murder, treason, repeated violent episodes, and sabotage against vessels, food stores or the Liveships themselves. Eusions also practice capital punishment; mutiny or hijacking starships is punished with execution. Exile is generally the preferred punishment, as any offspring an exile may have are welcomed back to the Fleet.

Cases involving treason are particularly rare, as Eusions are only accused of treason if their actions conceivably harmed the entire Flotilla, not just a single ship. The accused are given a hearing with the members of the Admiralty Board acting as judges, and if found guilty, they are sentenced to exile. If the treasonous act is deemed only a tragic mistake in judgment, the guilty party might be granted a small ship and supplies for their exile.

The empire has no political relations with the Eusions because the Migrant Fleet has not yet passed through any human-controlled area of space. Other species tend to look down on the Eusions for several reasons, the foremost of which being their supposed 'unleashing' of the Lasar upon the galaxy. This act led to the Eusions' losing their embassies in most places. Eusions are often viewed as beggars and thieves.

Because of the Flotilla's limited resources, Eusions strip-mine the systems they pass through, which often puts them at odds with any species currently settled there. The Migrant Fleet also tends to drop off criminals on planets it passes, because the Eusions cannot support a non-productive prison population—they simply lack the resources. However, life on the Migrant Fleet means Eusions have unique skills. They are masters at maintaining and converting technology, especially ship parts, and they are also expert miners because the Fleet requires huge amounts of fuel. They are able to repair what most species would melt down. This proficiency means corporations sometimes quietly hire Eusions “on the side” if the Migrant Fleet is nearby, replacing existing workers, much to their annoyance.

This unpopularity, and the fact their entire species travels and works as one, makes most Eusions quite insular, caring only about the continued survival of the Migrant Fleet. Their nomadic life and exclusion from the other races mean that the concerns of the otjer races don't particularly interest or impress them.

In the early years, many Eusion freighters were armed and used as irregular “privateers.” Civilian ships still show a strong preference for armament, making them unpopular targets for pirates. Indeed, it is mentioned that almost all ships in the Migrant Fleet carry ship-to-ship armaments of some sort and to varying degrees. Though they have rebuilt their military, there are still mere hundreds of warships to protect the tens of thousands of ships. The Eusion navy follows strict routines of patrol, and takes no chances. If the intent of an approaching ship can't be ascertained, they shoot to kill.

For this reason, young Eusions on their Pilgrimage are given code phrases to repeat upon their return, as they often arrive back in vessels they have bought or scavenged which are unknown to the Flotilla. One phrase denotes a successful Pilgrimage and the Eusion navy will permit them to rejoin the Fleet; the other alerts the navy that the Eusion is returning under duress, and their ship will be immediately destroyed.

The Eusion military utilizes weapons specifically designed to counter synthetics such as the Lasar. The Adas Anti-Synthetic Rifle is an electrical weapon optimized for medium and long-range firefights. Other weapons include the Arc Pistol, based on the Arc Projector, and the Reegar Carbine, a more powerful iteration of the Arc Pistol.