The Tau Empire is the small but rapidly expanding nation of the Tau, a young species of blue-skinned humanoids with very advanced technology. They are a relatively benign faction, striving toward a concept they call the "Greater Good" instead of enslaving or consuming the whole galaxy, but pursue it narrow-mindedly, and while they would not wipe out a world of civilians that refuses to join the cause, they might forcibly subdue it and brainwash the population.
Tau technology is a source of wonder, surpassing even the Eldar in some areas despite the species having a spacefaring history of only a few thousand years. Tau are not physically very robust, and their military tends to rely on heavy ranged firepower, but they do employ a number of allied species such as the Kroot and the Vespid in military roles not suited for Tau soldiers.
The Tau were originally a species of tribal hunter-gatherers living on the desert plains of T'au. An Adeptus Mechanicus exploration fleet discovered the world in M35 and found a sentient species at a Stone Age level of development. The Tau were dismissed as insignificant and scheduled for extermination, their world to be colonized by the Imperium. However, a Warp storm shortly erupted in the area, making T'au inaccessible, and it was soon forgotten.
Meanwhile, the primitive Tau went about their lives. At some point, the species became divided in several distinct races: the plains Tau, strong and skilled hunters; the mountain Tau with hollow bones and wing membranes; the river valley Tau with agriculture and metallurgy; and the wandering merchant-negotiators mediating between the tribes.
Eventually, avarice got the better of the Tau. Growing pains caused by their unusually rapid technological development led to sophisticated weaponry. The Tau of the river valleys built stone fortresses and black-powder weapons to ward off the aggressive plains Tau. These fledgling skirmishes led to the darkest period in Tau history, the Mont'au. The wars that broke out lasted for years, thousands dying from famine and plague as well as fighting. The Tau were on the verge of wiping themselves out. Out of the destruction and darkness of the Mont'au came a guiding light: the Ethereals.
The Ethereals first appeared during the siege of a city called Fio'taun. For five long years the fortress city had held off assaults of the plains Tau with their walls and cannons, but disease and starvation began to take their toll. As the tide of the siege turned, two mysterious Tau appeared. One made his way into the camp of the plains Tau, exuding a quiet authority that no Tau was able to resist. Soon, the leader of the plains warriors was persuaded to parley with the Tau of Fio'taun. Similarly, the other mysterious Tau made his way deep into the fortress. Within a few short hours, the gates stood wide open, and the Tau stood ready to talk.
The Ethereals spoke of the importance of peace and understanding between all Tau. They described a Greater Good that each Tau must strive towards. The besiegers and the besieged quickly agreed with the Ethereals and a truce was reached. Across the land, Ethereals emerged, each with the same quiet authority and message of harmony. With the Tau united, a great civilization began.
The introduction of the Ethereals to Tau society led to a rigid caste system, with each caste named by an element close to them. Thus, the warriors became known as the Fire Caste (Shas) due to their fiery temper. The artisans and scientists became the Earth Caste (Fio), being the most pragmatic. The diplomats and administrators became the Water Caste (Por), as water flows through all life, uniting it. Lastly, the messengers and spies became the Air Caste (Kor), traversing the land on top of gusts of wind. With the invention of aircraft, and later spacecraft, the Air Caste would become the pilots of the Tau.
Under Ethereal leadership, the Tau soon gained spacefaring technology and started colonizing nearby worlds. The first stage of expansion covered the core worlds of the Tau Empire; Tau'n, D'yanoi, Bork'an, Dal'yth, Fal'shia, Vior'la and Sa'cea. Each colony – called a "Sept" – developed its own cultural identity, "flavor" and traditions.
The second phase of Tau expansion led to contact with Imperial frontier worlds. Relations were at first peaceful, with Water Caste negotiators exchanging goods and technology with the humans. This soon drew the Inquisition's attention, and in 742.M41 a fleet was deployed to assert Imperial authority. A major conflict known as the Damocles Crusade ensued, with the Imperium deploying 19 Imperial Guard Regiments and almost a dozen Space Marine Chapters to push back the Tau and stop the expansion. The Imperium pushed deep into Tau space, but resistance near the core worlds got too heavy for a fast victory and the first signs of Hive Fleet Behemoth ended the conflict; the fleet was ordered to evacuate immediately and the Tau decided not to harass.
An uneasy peace with the Imperium ensued, the Tau completing their second expansion phase with the occasional conflict. The Kroot, Vespid, Nicassar and Demiurg species joined the Tau Empire at some point. The Tau had their own Tyrannic war as Hive Fleet Gorgon, a splinter fleet of Behemoth, invaded in 899.M41. The Tyranids were destroyed by Tau and Imperial forces a few years later, after losing several colony worlds.
In late M41, the Tau are in the process of securing third phase colonies, while fending off remnants of Hive Fleet Kraken and the occasional Ork raid. They have an uneasy relationship with the Imperium, which is more concerned with larger conflicts such as the Armageddon wars and the 13th Black Crusade.
- T'au (all games)
- Fal'shia (Dawn of War: Soulstorm)