An insectoid race native to Suen. Thought extinct at least twice, they have reemerged as a significant local power and allies of the geth.

Wikia Rachni kuva

Rachni Queen, circa 2186.

Caste System, Overview

The foundation of rachni society, the caste system encompasses four distinct subspecies: drones, soldiers, brood warriors, and queens. The intelligence and autonomy of the castes increases in direct proportion to its importance within the Hive’s structure: a rachni is only as intelligent as it needs to be.

A Worker is a programmed unit. A Soldier is a distinct individual with their own potential, tastes, desires, and motivations, but with the intelligence on par with a crow or dolphin. Brood warriors and queens are fully-realized personalities, self-aware and intelligent; they are distinct from the rest of the hive and the closest, as much as the rachni can be, to the other species of the galaxy.


The rachni worker is a small arthropod approximately the size of a housecat, and is omnipresent within any rachni structure from ships to military bases to sprawling Hive clusters. More akin to living drones than truly sapient creatures, the Worker functions via an intuitive understanding of complex tasks and mechanisms, a process believed to be an application of the rachni’s genetic memories. A worker does not understand how a nuclear fusion reactor works, for example, but provided sufficient materials and time it can assemble a functional model.

Workers populate hives in massive swarms up to thousands apiece, descending upon tasks dictated to them by members of higher-ranked castes. Despite their unsettling appearance, they are usually harmless, though they possess a biological self destruct mechanism: an explosive burst of corrosive, toxic chemicals. In times of conflict they can be deployed en masse to defend a Hive, weakening enemy ranks before the arrival of more organized units, and prepare ambushes.


While workers form the bulk of a Hive’s population, the soldier caste is the true backbone of the swarm as they perform nearly every task that requires a complex skillset. Possessing intelligence on par with corvids or primates, soldiers serve most prominently in a combat capacity: provided with the tools for a clear, concrete objective, they will coordinate tactically to reach it. Soldiers operate on the local level, with strategic thought and high-level coordination left to queens, brood warriors, or brood auxiliaries. Outfitted with integrated weaponry, partially organic armor, and the accumulated skills of generations of warfare, they are a potent force on the battlefield.

Fearless, hardy as krogan, and capable of acting in concert on a vast scale, the reappearance of rachni soldiers has stirred up unpleasant memories within Citadel species. However, rachni soldier castes serve in more roles than combat alone, including as scientists, worker-caste coordinators, engineers, pilots, and attaches. A soldier is not trained in its role, but programmed: those with the activated information of a pilot, for example, will instinctively comprehend how every part of its ship functions, how to employ it in its most effective role, and, of course, how to pilot it.

Outside those very specific, narrow areas of expertise, soldiers are perceived to be as intelligent as an ape or dolphin. Comparable to savants, they are more accurately templates: hard drives with carapace and limbs, able to fill virtually any need a hive has. Contrary to pre-existing ideas of insectile races, soldiers are resources that are conserved and committed with care, rather than expended in mass wave tactics.

Brood Warriors

Brood warriors are the first rank within the hive structure to possess true sapience as commonly understood, sitting directly beneath their queen within the hive’s hierarchy. They are the queen’s lieutenants, her geneticists, her ambassadors, her bodyguards, her field commanders, and her advisors. Brood warriors are born into their status, selected by their mothers in the egg and elevated before they hatch. Their growth is tailored by hormones, their mind cultivated by the queen’s song.

For every brood warrior the mother lays, there are a dozen who share their development whom are “muted” at the last step. These “brood auxiliaries” are an in odd position within the hive: significantly more intelligent, capable, and autonomous than a soldier, but unable to employ the expanded cognitive facilities of their elder brothers, such as the detailed genetic memories and innate understanding of how to orchestrate entire swarms. In the event of a brood warrior’s death, these junior males act as a safeguard: their latent traits engage, and they ascend to full brood warrior status. Otherwise, auxiliaries serve as an active brood warrior’s aides, direct subordinates, and immediate support.

Brood warriors are capable, articulate, and cognitively formidable, capable of devising and articulating strategies and tactics, designing and implementing rachni biotech to their soldiers, and orchestrating hive-wide industrial activities. Much like the queens, brood warriors have access to extensive genetic memories, albeit solely from their ancestral male line. Every brood warrior alive retains memories and knowledge of how to wage a macro-scale interstellar war. Further, in the event of a queen’s death, they act as a safeguard against complete hive destruction: their songs stabilize and calm the bloodlines while a new queen is hatched, typically from the same bloodline or dynasty as her late sister.

Physically, brood warriors are intimidating. Towering over the rank-and-file soldier caste at an average of ten feet standing, a Warrior possesses thick natural armor, powerful claws and tendrils and, unlike Soldiers, often has access to potent biotic capabilities. Genetic material of brood warriors is structured to encourage mutation, augmenting a hive’s diversity in order to offset issues from the rachni’s dramatically reduced gene pools - an important trait to a species that has had to survive multiple population bottlenecks.

There are many brood warriors to any given queen, and that number is often an unofficial sign of status between broods. Each male commands part of the hive’s population, namely the part that the queen has birthed utilizing his genetic material. Within this “firqa” he can inspire morale, issue direct commands, and modify the “templates” of soldiers. The specific nature of a firqa varies wildly from hive to hive: some queens prefer males that are jacks-of-all-trades, overseeing vertical slices of the Hive’s infrastructure and forces, while others prefer males that are specialized to perform within a specified field. No matter how a hive is divided up, male competition for the queen’s favor is a consistent fact of life.


A rachni queen is the heart and soul of her brood and hives. She creates the song that teaches and unites them. She carries the memories of her mother and all the queens before her, of her father and all the brood warriors before him, encompassing the whole of her direct family’s history in her genetic memories. She sets the course, infrastructurally, economically, militarily, and diplomatically. She commands near-absolute loyalty among her children and her brood warriors. With one order, an entire hive will die for her, throwing themselves into the teeth of enemy fire, but rare is the queen that will stoop to such brute and uncaring tactics.

Perhaps the most terrifying revelation from the galaxy’s reintroduction to the rachni is that a queen can play the game of politics, power, and dynastic bloodlines as well as any salarian dalatrass. This isn’t to say a queen is above armed conflict, for nothing could be further from the truth: when open confrontation develops, it is the queen who commands and orchestrates the war effort.

While the rachni are not a hive mind in the strictest sense, of one mind with many bodies, a queen nevertheless commands tremendous respect and deference from her children, lessers, and fellows. These instincts are formed from biological directives, heavily reinforced with cultural and social constructs. Intrahive conflict is so rare as to be almost unheard of, even if interhive conflict is a given fact of life within the Rachni.

Queens can shape the development of their children in the egg. Their hormones determine the caste and physical traits. The quality of the mother’s song determines an individual’s mental and cognitive capabilities. This song gives rachni purpose, knowledge, and engenders a healthy psyche. In the formative stages, an absent song can give rise to psychological trauma or even cause the rachni to revert to a feral state. These capabilities are ambient mechanisms, allowing the queen to afford as much or as little attention as she needs to each of her innumerable eggs, while she addresses other matters crucial to the hive. The soundproofed birthing chambers are her fortress, her inner sanctum.


Rachni hives are noisy affairs, full of chittering mandibles, scuttling legs, and the omnipresent music of the city. Notes and songs sprawl across the breadth of rachni perception, existing as not only tones but also entire palettes of color and reams of raw information. Every rachni has a name, a musical cadence that identifies them and their purpose. Worker names are short and sharp, frequently strung together into larger collectives to reference the swarm they’re in at the time. Soldier names are longer snippets of a greater melody, modified by their alterations and current roles. Brood warriors and queens have even longer, grander names, lyrical and rich. The further that one pulls back, the more the distinction between name and song blurs: even hives have names, a unique song that’s woven under the endless singing. The complexity of dynastic names is based upon their power, the duration derived from the length of their history.

Between pheromone exchanges between individuals and the full range of sounds both audible and inaudible, it is rare when anything approaching silence occus in a hive. To the rachni, silence is stillness. Silence is death.

The existence of organic QEC’s between queens and their sons and daughters is a popular theory and not without basis in history: the rachni have been exposed to at least two galactic superpowers, the Reapers and Protheans, who modified and tailored the species to suit their needs. However accepted this fact, the degree of interconnectivity between members of upper and lower castes is hotly disputed within the xenobiological community.

Rachni themselves generally tend to employ long-range communication devices the same way as other species, albeit with organic and pseudo-organic components.


The politics of the rachni are characterized by conflict and competition. The heart of rachni politics is the hive - the direct holdings of a queen, along with her immediate children, brood warriors, and all the infrastructure within. Hives can range from small city-states to sprawling, multi-planet domains. One step above the hive is the brood, composed of both a queen’s personal holdings and of all those she commands indirectly, such as loyal daughter-queens, weaker hives that have pledged allegiance, and bloodlines that she has married her sons and daughters into. Broods can range from collectives the size of a star system to - at the historic height of rachni expansion - entire star clusters. The largest power structure within rachni society is the dynastic line: the collected power of dozens, if not hundreds, of related hives and broods. At the very top of a dynastic line is the Ostad-, or Conductor-Queen: the queen with enough power to assert supremacy over any and all others. For this she possesses the ability to command her lessers (with varying degrees of enthusiasm) and may shape and direct the course of her extended family and subordinates. Beneath her is the Choir of Queens, the leaders of the most powerful broods within the dynastic line. It’s from their ranks that the Ostad-Queen typically rises, and to where she recedes when overthrown or otherwise deposed. Past the upper levels and often within broods themselves, the structure is far more fluid. Secondary and tertiary queens rise and fall with their Hive’s wealth, influence, and fortunes in war. Combat over resources, territory, and prestige, an accepted fact of rachni politics, are made easier with the knowledge that the rachni’s aims are more often assimilation than eradication. The time-honored tradition of trading bloodlines and alliances, matching prospective brood warriors (and accompanying auxiliaries) with eligible queens and all the political machinations bound within, is simply another facet of the endless jockeying for power and prestige.

The reigning queen currently keeps the peace by virtue of a small population, coupled with tremendous personal respect. She is the mother of the entire species, delivering them from the brink of extinction. To dethrone her is nearly a sacrilegious thought to her daughters and sons. She is the sole Ostad-Queen and monarch of her race and, for now, wields uncontested power throughout the Hives.


Rachni technology is a fusion of the organic and synthetic. The synthetic portion generally comprises the skeletons of infrastructure and core components, such as accelerator weaponry, starship frames, engines, and the frameworks of buildings. Organic parts are engineered to fill the muscle and sinew around this synthetic “skeleton”. In a rachni cruiser, the frame is alloy, the engines and drive core and reactors mechanical. However, the wiring of the ship is derived from neural tissues, the life support is a symphony of tailored microorganisms and environmental checks and balances, and the piloting systems synchronize with their soldier crews. Weaponry balances heavy accelerator cannons with symbiotic creatures that live within the superstructure of the ship itself and are fired at enemy capital ships in heavily armored breaching pods.

The vast majority of rachni engineering derives from genetic modification and enhancement, and it’s difficult to tell where “biological augmentation” ends and “living technology” begins. The upgrade packages that a soldier may receive from his brood warrior could incorporate symbiotic, partially-living armor with a cocktail of genemods. Infantry fighting vehicles and “tendril-tanks” take cues from organic form and function. Coupled with their skill at enduring, manipulating, and creating environments whole-cloth, the rachni have since emerged on the galactic stage as a potent force in genetics and environmental engineering.

See: Sykalid.


The rachni economy is self-sufficient. Swarms of workers and soldiers burrow through the crust of planets as fast and as effectively as modern machinery, extracting minerals and natural resources. The technology they utilize is extensively tailored for and produced within the Hives themselves. Trade value is thus associated with tangible assets: processed minerals, choice territory, eligible bachelors and bachelorettes, and luxuries such as spices, unique songs, precious metals, and feats of “artistic genengineering”. Such luxuries are the domain of the upper castes.

Queens and brood warriors trade between hives and broods, leveraging access in an effort to acquire ever grander and more impressive displays of success, power, and prestige. A queen who can afford to have spicy-sweet habala roots with her meal is a subject to the jealousy and admiration of queens who cannot. A brood warrior with genengineered living battle armor is considered a marvel of artistic construction and is respected and envied by his fellows who have no such thing.

Early History

The rachni evolved on Suen, a planet tidally-locked to its red dwarf star. Life developed in a habitable terminator zone between hemispheres that were constantly scorched or perpetually frozen. The harsh conditions of Suen’s surface forced the rachni to forage underground amid sprawling subterranean river systems.

Sometime at the height of the Prothean Empire, the Protheans discovered the rachni and bred them as weapons of war, selecting the most cunning and warlike queens and unleashing rachni swarms on their enemies. Eventually, the rachni became too difficult to control; they turned on their Prothean masters and overran multiple star systems. The Protheans attempted to eradicate the rachni and destroyed as many as 200 worlds before they were satisfied the threat was eradicated. However, enough members of the original rachni survived on Suen to replenish their population.

Rachni Wars

The conflict known as the Rachni Wars began when salarian explorers opened a mass relay leading to Suen's star system.

The rachni used extensive research on element zero gathered from Kashshaptu to reverse-engineer the FTL drives of the explorers' starships. They proceeded to construct FTL vessels of their own and rapidly expanded into the galaxy.

Attempts by the Citadel races to negotiate were futile, as it was impossible to make contact with the queens that guided the race from beneath the inhospitable surface of their homeworld. It was assumed that the rachni were irredeemably hostile and could only be stopped through warfare, but the rachni had the upper hand and overwhelmed defenses with their sheer numbers.

This period saw the Citadel races fight a losing war against the rachni for nearly a century until the salarians "culturally uplifted" a new species, the krogan. The volatile krogan homeworld, Tuchanka, had been ravaged by a nuclear winter caused by a krogan civil war. The salarians helped the krogan by giving them advanced technology and relocating them to planets not cursed with lethal levels of radiation, toxins or deadly predators. The true purpose of this salarian altruism soon emerged; the krogan were needed in the Rachni Wars as reinforcements. Unlike most Citadel species, the krogan had an extremely rapid breeding cycle. They had not only the numbers to drive the advancing rachni back, but the ability to endure the harsh conditions of the rachni planets.

Clan Korwun were highly active in the Rachni Wars, claiming several notable victories on the Mashari Campaign, but were often reprimanded for their disregard for other clan’s soldiers and their overzealous pursuit of victory at any cost. In response to such accusations, the then-leader of the Korwun, Clan Lord Sosek, is reported to have said “You want peace, but do not want to pay the price. We will pay it for you, do not question how we do so.” This attitude eventually resulted in a life-long blood feud between the Korwun and the neighbouring Clan Vynchar, with whom they already had an age-old rivalry. Sosek convinced Clan Lord Rawn of the Vynchar to commit a battalion of his troops to a frontal assault on a Rachni hive, only for clan Korwun’s cruisers to bombard the entire site from orbit, destroying not only the Rachni but also the Vynchar warriors. Although the Korwun insisted that the fault lay with the Vynchar, whom they alleged broke formation and charged the Rachni after the bombardment had already begun, many believe it was a plan by Sosek to reduce the Vynchar numbers.

When krogan fleets pushed them back to Suen, the rachni refused to surrender. The krogan response was swift and brutal: they bombarded Suen’s cities and detonated powerful bombs in the rachni’s underground nests, creating massive sinkholes on the planet’s surface.


During the Reaper invasion, a single queen, hatched from an egg that survived the Rachni Wars, made contact with the Systems Alliance. It offered assistance to the Crucible Project in exchange for the cessation of hostilities with Citadel races. The queen migrated to the Ninmah Cluster before the Crucible fired, and disappeared from the Council’s detection for several years.


Post-Reaper War, the rachni returned to galactic politics in spectacular fashion, appearing with a battle fleet over Suen without warning. A significant hive network was reestablished on Suen, along with secondary bases on Kashshaptu and a framework Helium-3 grid above Damkianna, plus an undisclosed number of tertiary hives (with associated Queens and their retinues) on Maldor, Inakhos, and the moons of Daganshtan. According to reports from on-side journalists, a Queen and her guard boarded Listening Post X-19 as part of what appeared to be a diplomatic mission, and she was soon in communication with the Commander of the Listening Post, one Deix Resocanthias, who had been demoted and assigned to the Post as a result of controversy over his judgment during the Reaper War (in withdrawing his forces and the Terminus irregulars under his command at the expense of the life of the planetary governor they were assigned to protect). Quiet attempts by the Turian Hierarchy to replace Commander Deix during these proceedings were rebuffed by the rachni Queen.

The return of the rachni sent shockwaves through the galaxy. A geth Consensus naval battlegroup was dispatched through the Pangea Expanse Relay, independently of formal Conclave decision. A Council mission - a turian battlegroup - arrived shortly thereafter. A week-long standoff around the Listening Post de-escalated with the arrival of the Consensus forces, who reaffirmed rachni statements of nonaggression. Diplomatic packets dispatched via the Listening Post and Consensus communication nets outlined the basic requests of the rachni regarding the galactic community. First and foremost, the Ninmah was to be recognized as sovereign Hives territory, under the express authority and control of its Queens. Secondly, the rachni and the geth had engaged in a mutually recognized defensive pact and protected trade arrangement, subject to their individual purview. Thirdly, the Hives were collectively open to treaties of non-aggression with Omega, Khar’shan, Tuchanka, and the Citadel.

The fallout, understandably, was rather extensive. On Rannoch, the Quarian Conclave and Admiralty Board descended into bitter factionalism over how to best respond to a move that Gah’rilya vas Sekith, Captain of the namesake heavy cruiser and a significant minority leader within the administrative body, publicly decried as “tantamount to usurpation”. The Citadel Council spent the day sequestered in an emergency session, while Omega and Khar’shan remained mute as to their intentions. On Tuchanka, an Urdnot-hosted Crush deteriorated into substantial infighting as a result of unrelated grievances.


Unleash the Swarm: Nikolai Aleksanders doesn't feel that the current rachni situation is useful.

The Rachni Return: CDN discusses the rachni revival immediately after the race makes contact with the galactic community.

Breaking News: Yes, the rachni are back... and partners of the geth. Discuss.

An Offer You Can Refuse: Diplomatic Immunity (Albert Lowell) invites Kayana Pesh to join him on his mission to the rachni hives.

We Come In Peace: CDN and the galaxy make contact on rachni home soil.

Brass, Blood and Bridesmaids: A rare glimpse into life on Suen.

Suen Hive Seeks Arts: An odd request from some of the rachni.