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"Our conquest is inevitable, our ascension a matter of time. Let none who are wise deny our destiny."

Aun'Va, Ethereal Supreme

T'au Fire Warriors led by an Ethereal during the First Sphere Expansion.

The First Sphere Expansion is the name given to the colonial expansion that marked the rise of the emergent T'au Empire as a major star-faring species of the Milky Way Galaxy through its first organised effort at interstellar exploration and colonisation.

The First Sphere Expansion saw the T'au establish their stellar empire and settle new colonial "Sept worlds" in the Eastern Fringe of the galaxy. This thousand-year-long period, known to the T'au as "The Great Expansion," occurred in 502.M37-956.M38, and was considered a time of great scientific advancement and cultural renaissance.

It was during this period that the T'au first advanced into space, colonising planets as far as their conventionally-driven, sublight voidcraft would take them. The notion that the T'au's future lay in the stars was keenly grasped by all of the T'au castes at this time, after which the T'au began to push their realm outwards at an explosive rate.


On the Eastern Fringes of the galaxy, there is a new power on the rise. The T'au Empire is spreading; its boundless ambitions have yet to be checked. Although world after world have been subsumed under their control, the T'au believe it is only the start of their new unified order, for it is their destiny to rule the galaxy, and none have the right to deny their progress across the stars.

The T'au are a dynamic race, whose unity of purpose and superb grasp of advanced technology have enabled them to make rapid advances. Where once the T'au looked up to see the distant pinpricks of unexplored stars, now they see the shimmering lights of their own interstellar empire. The T'au believe that their destiny is to rule the galaxy and that the time to do so is now.

They fully accept the superiority of their culture and technology, and have recognised that they are the only hope of bringing an enlightened philosophy to an otherwise bleak, barren and backwards galaxy. There is no feat beyond the range of their engineering, no quandary that their scientists cannot solve, and no foe that their warriors cannot overcome. In time, all other intelligent races of the galaxy will come to accept these truths, and the very stars will be reshaped and realigned in the name of the one cause that ever mattered.

The T'au are driven by their adherence to a singular ideology -- the Tau'va -- which translates as "the Greater Good," a phrase that means that the good of the many in society must take precedence over the selfish desires of the individual. That one must set aside personal desires to work for the Greater Good is of prime concern to the T'au and it is impossible to underplay the importance of this ideal -- all working together to achieve the advancement of the whole society.

Advanced Evolution

The story of evolution from stone tools to a more advanced society is a common enough tale for many sentient species throughout the galaxy. What makes the T'au story notable is the speed at which their culture leapt from age to age. It was not many generations after they established their first settlements on their homeworld of T'au that the T'au began building fortresses and using black powder-based combustion firearms to defend them from marauding tribes of plains dwellers allied with the T'au of the air. The T'au had entered their darkest age, when the entire race was being destroyed by war and disease. At this time, strange lights were seen in the sky and many believed these were signs that they were living in the last days -- that extinction was nigh.

From these times come many different myths of how the race was pulled back from the brink of annihilation, the foremost legend of which was the "Ethereals of Fio'taun." In this tale, T'au of unusual appearance gathered the leaders of the various rival cities and brought them to a great gathering. As the enemies met, the newcomers, who called themselves Ethereals, bade all to sit. Beneath a maiden moon of purest white, they began to speak. The mysterious strangers explaining that the skills of each tribe were unique and should be harnessed, and they spoke of a Greater Good that could be achieved if only they would put aside their feuding ways and instead work together. The two strangers talked through the night, their words heavy with great power. As the sun crested the horizon, a truce was agreed between the warring factions. Soon, more Ethereals appeared and their message of the Greater Good spread to every corner of the planet.

The new philosophy took hold quickly. Soon the internecine wars were over, and the T'au flourished as never before. T'au society was formalised into castes, each known by the mythological element that most befitted its role in the Greater Good.

Dynamic Expansion

The T'au entered into an unprecedented period of rapid change heralded by new inventions and great leaps of advancement in many fields. Each caste became relentlessly driven in its pursuit of the next achievement for the Greater Good. The successes that followed were plentiful -- with rapid advancements discovered in metallurgy, engineering, energy production and weapons manufacturing. With breakthroughs occurring almost daily and hardship and disease greatly reduced, the world of T'au was soon showing signs of overcrowding. Again, the Ethereals had the answers, and pointed towards the stars.

At their bidding, the Earth Caste began building and testing chemical rockets; the Air Caste began training for their new roles as void pilots. The notion that the T'au's future lay in the stars was keenly grasped by all of the castes. After the first few rockets successfully escaped the planetary atmosphere, the T'au rapidly moved to establish orbital communities, followed by a base on Lu'val, the nearest moon of their homeworld. Scouting voidships, probes and far-ranging scanning devices were sent deeper into space.

The T'au ascertained that their world resided in a tightly packed star cluster with scores of planets in close proximity to each other. Scans reported that many of these worlds were capable of sustaining life. The construction of a massive orbital dock allowed larger space-faring craft to be built and soon colonising efforts were underway -- the nearby planet of Tau'n became the first of these bold new enterprises.

The Spheres of Expansion

The rise of the T'au can be seen to develop through three distinct phases, periods of intense growth known to the T'au as "Spheres of Expansion". Each of these waves of colonisation is marked by a long build-up of resources, after which continual waves of exploratory missions are launched, followed, where needed, by military campaigns to solidify territorial gains. Once a T'au colony transforms itself into a stable settlement, it then serves as a jumping-off point for the next expansion. By the end of the millennia-long First Sphere Expansion, as it later came to be called, the T'au Empire had unfurled across the heavens and consisted of eight fully settled systems known as Septs.

Named after its primary or "Sept world", a Sept can include any number of additionally colonised planets or moons, as well as other holdings such as listening posts, sensor fields, shield satellites, orbital cities, and mining operations. Everything is connected, both by a series of space stations and a massive net of communications and sensor relays strung between major locations. Although it might take many generations to establish itself, each Sept is unique, with its own cultural nuances and varying proportions of the different castes and T'au-allied alien populations.

A Destiny to Rule the Stars

The T'au continued to push their realm outwards at an explosive rate during the First Sphere Expansion, although losses were high amongst these early explorers. Not only did space travel and new and unusual environments take their toll, but as they ventured further from their homeworld, the T'au also began to encounter alien beasts, many of which proved dangerous. At last came the time when the rigorous training of the Fire Warriors could prove its worth. The colossal reptilian beasts of D'yanoi consumed many T'au colonists, before the quick deployments and disciplined volleys of the Fire Caste drove the monstrous creatures back.

On Sa'cea, the desert planet was so overrun with fierce, flesh-eating predators that the Fire Caste had to hunt down and destroy them all before settlers would even dare to land. During these early expansions the T'au also encountered intelligent alien races -- whole civilisations of other sentient creatures. While the Fire Caste sought to destroy any who opposed them, hunting them in the same manner in which they eradicated savage creatures, the Ethereals saw an opportunity to bring enlightenment instead of war. Just as the Ethereals had stopped the fighting on T'au and bound the tribes to work towards a common purpose, so too should the aliens be embraced and given a chance to contribute to the Greater Good.

The Ethereals guided the other castes to accept these alien races, no matter how strange. It did not matter whether these new aliens were mired in barbarism, enslaved to crude superstitions or simply unaware of the magnitude of the great destiny unfolding before them, the Ethereals said all should be welcomed into the emergent T'au Empire.

The Ork Threat

The T'au first discovered Orks on the planets surrounding their first major colony, Tau'n. Signals soon arrived reporting disparate Ork tribes scattered across every star system they investigated. The sophisticated T'au quickly learned to pinpoint the telltale Ork signature on their scanning equipment, and it appeared with alarming regularity on planets, moons, asteroid belts and virtually anywhere that could support life. It took many battles before the T'au at last abandoned their futile attempts to absorb Orks in the manner that had proven so successful with a dozen other alien civilisations; there was simply no bargaining with such creatures.

The Ethereals themselves eventually conceded that these aliens were a lost cause and amended the protocols to forego any attempt to integrate the Orks into the Tau Empire, declaring, at last, that the Greater Good was actually served by eliminating the Greenskins.

Fortuitous Discovery

An Ethereal, escorted by Fire Caste warriors in T'au Battlesuits, arrives on the Kroot homeworld of Pech.

At the close of the first period of T'au expansion, an exploration fleet out of Dal'yth picked up long-ranged scans of Ork ships firing on Kroot Warspheres. The previously unencountered Kroot were defending their enclave on the planet of Krath, although they were hopelessly outnumbered. Intending only to observe, the T'au were drawn into the battle as both the Air Caste Admiral and Fire Caste Commander could not bear to watch the honourless Orks bludgeon their way to victory. Quickly deploying their superior fleet, the T'au destroyed the ramshackle Greenskin ships.

Too late, however, they realised that this was merely the vanguard of a mighty invasion force that was closing on them in an encircling pattern. Thus began an extended war, both in space and over several planets, later named the War in the Place of Union, for it marked the first time the T'au and Kroot fought side by side. So effective was the sudden alliance that they withstood the Orks long enough for reinforcements from Sa'cea to arrive, and ultimately triumphed over the Greenskins. The T'au were so impressed with the Kroot's fighting prowess that they agreed to extend the alliance in order to liberate the remainder of the Kroot enclaves, who were also under Ork attack.

For the next ten Terran years, the T'au helped drive all sign of Orks from the Kroot worlds, eventually coming to the Kroot homeworld of Pech at the behest of the greatest of Kroot leaders, the legendary Anghkor Prok. There, at the sacred Oathstone, the Kroot leader swore allegiance to the T'au Empire and pledged his warriors to fight for the Greater Good (and regular payment). That pledge, and the cooperation between the two races, is still honoured today. The Kroot are, by far, the most common alien auxiliary force to serve in T'au armies. The T'au greatly value the military service of the Kroot, although they continue to hope that exposure to their own superior culture will eventually cure the Kroot of their cannibalistic tendencies.

First Sphere Expansion Timeline

The T'au have developed their own mode of timekeeping based on the annual cycle of their homeworld of T'au aound its star, a unit called a tau'cyr. Except on human planets that are still in the process of being subsumed into the T'au Empire, the T'au do not use the Imperium's dating system. However, for ease of translation, it has been employed here:

  • The Great Expansion (502.M37-956.M38) - A time of great scientific and cultural evolution during which the Tau first advance into space, colonising planets as far as their conventionally-fuelled voidcraft will take them.
  • First Colony (533.M37) - The T'au colonise their largest moon, Lu'val; this is their first off-world holding.
  • Tau'n Established (756.M37) - The Ethereals declare the colonies centred around the planet Tau'n will become their own Sept -- or realm, governed centrally from Tau'n, the prime Sept world. This is the first of many star systems to be colonised.
  • Welcome Additions (893.M37) - The Poctroon become the first sentient alien race to join the T'au Empire, although within a few generations, disease destroys their indigenous population. The T'au, whose physiology is fortunately immune to the plague, inherit the Poctroon homeworld, turning it into the prime world of what will become the Bork'an Sept. The Nicassar become the first race to join the T'au Empire and survive long enough to tell about it.
  • The Campaign of Cleansing (606.M38-792.M38) - This period marks the first prolonged T'au campaign against the Orks. The T'au suffer many defeats but are ultimately able to eradicate the Greenskins from the territory of the First Sphere, thanks in part to the Earth Caste refinement of the first Pulse Rifle. The Dal'yth Sept is founded.
  • The Union of T'au and Kroot (844.M38) - In order to combat Orks, the fortunate alliance between T'au and Kroot is established. Within a decade, the Water Caste has established embassies upon Pech , the capital world of the Kroot realm.

First Sphere Expansion Septs

The sigils of the First Sphere T'au Septs

The First Sphere Expansion of the T'au Empire began shortly after their species first achieved spaceflight capability. The T'au homeworld and the First Sphere colonies are of major economic and political importance to the T'au, and form the hub of the T'au Empire.

  • T'au - T'au is the birthplace of the T'au species, and it is here that the High Council, formerly led by the Ethereal Supreme Aun'Va, convenes, its decrees shaping the entire T'au Empire. T'au remains the centre of T'au culture and the empire's bureaucracy, and produces many Fire Caste warriors. No other sept can rival T'au for prestige, and only Vior'la can match its power.
  • Tau'n - The first T'au Sept established in the Empire's history, Tau'n has a chain of enormous orbital docks and controls the largest of the Air Caste space stations; every sept hosts warships of the T'au fleet (Kor'vattra), but none can boast of more than Tau'n.
  • D'yanoi - Named after the twin moons of its prime Sept world, D'yanoi has survived long isolation due to a Warp Storm of fierce and unnatural qualities. It has also seen many infamous Ork invasions. Having been isolated for such a long period of time from the rest of the T'au Empire, its inhabitants are considered somewhat rustic and backwards.
  • Bork'an - The Sept of Bork'an is a centre of T'au learning and academia, and its system has many rich mining planets. Bork'an has a high percentage of settlers from the Earth Caste, and Fire Warriors from here are not infrequently outfitted with prototype weapons and equipment developed by their Earth Caste counterparts.
  • Dal'yth - The Dal'yth Sept was ravaged during the Damocles Crusade; many of its outer colonies and several cities on its prime Sept world were destroyed. It has recovered quickly, thanks to its busy trade ports. Large numbers of aliens can be seen here alongside its famously efficient Water Caste merchants and diplomats.
  • Fal'shia - Many technological innovations have come from this Sept. Fire Caste warriors from Fal'shia are often the first to try out prototype weapons, armour and system upgrades.
  • Vior'la - The planet Vior'la orbits a binary star and its name translates as "hot-blooded" in Low Gothic. It is known to produce especially aggressive and skilled T'au warriors. Many Ork invasions have been broken by the Sept, and some of the most respected Fire Caste academies reside upon Vior'la.
  • Sa'cea - The prime world of Sa'cea is the hottest and most densely populated of all T'au worlds. As a result of its large population, Sa'cea has produced more colonisation fleets during the Second Sphere Expansion than any other. Warriors of Sa'cea are regarded as particularly honourable.

See Also


  • Codex: Tau Empire (6th Edition), pp. 9-13, 28
  • Codex: Tau Empire (4th Edition), pp. 6-8, 10
  • Codex: Tau Empire (3rd Edition), pp. 6-8