Editing Setting:Brighthammer 40,000/1st edition (section)

=== Tau ===
An automated Imperial survey probe discovered the Tau roughly six thousand years ago, and found a race of plains-dwelling aliens who had just mastered fire and lived in simple, hunter-gatherer societies.  An expedition was sent to offer the xenos the Imperium's friendship, but a sudden and unexplained interstellar storm of immense power enveloped the sector, cutting it off from the rest of the galaxy.  These storms have recently abated, and a follow-up survey has shocked the Imperium - in only six millennia, the Tau had been transformed from a peaceful but primitive civilization to a fascist, expansionist, star-spanning empire possessing advanced technology and insatiable bloodlust, making them one of the greatest threats facing the galaxy.

Somehow, the Exodite Eldar had come across the young Tau and proceeded to manipulate and mold the Tau into creatures more like themselves.  For centuries the Exodites set various petty Tau kingdoms and city-states against each other, plunging their world into chaos which nearly wiped out the race.  But then the Exodites capriciously changed their minds, and decided to unite the Tau under one order.  Using blasphemous bio-engineering, the Exodites bred a subspecies of Tau that possessed the pheromone glands of an insectoid alien race, granting them absolute control over other Tau.  These "Ethereals" became the Exodites' mouthpieces in Tau society, and with the help of Eldar technology quickly built a brutal world government before spreading into nearby star systems.

'''Tau Society''' 

Tau society is strictly divided into a caste system, supposedly a society of equals, in reality a strict hierarchy.  The '''Earth Caste''' are the lowliest Tau, slaving away in terrible conditions to keep the empire supplied with the wargear and supplies that fuel its aggressive expansion.  The luckiest of the Earth Caste get to work on miserable farms and live in hopeless drudgery; the unlucky ones are sent to hellish factories, where maimed workers are thrown out in the streets to die.

The '''Water Caste''' are derided as conniving and untrustworthy schemers, merchants and diplomats who cheat and swindle those they come across.  They mostly prey on too-trusting human societies bordering the Tau Empire, selling malfunctioning and downright dangerous equipment for outrageous prices, then laughing when their customers are killed or crippled after their purchases blow up in their faces.  Worse, the Water Caste also attempts to convince human worlds to renounce the Emperor’s benevolent rule for the empty promises of Tau society, bringing in new worlds of unwitting slaves for the Tau Empire.  For this reason, the Imperium has forbidden its citizens from dealing with the Tau, and dispatched Special Agents to borderworlds in order to protect people from these charlatans.

The Tau’s '''Air Caste''' are haughty and cowardly, preferring to rain destruction from far above their enemies rather than engage in a fair fight.  They provide pilots and crews for the Tau’s navies and build the starships that allow the empire to expand, but the rest of the Tau view them with distrust at best.  The Air Caste are notorious for launching unprovoked and unannounced orbital bombardments on defenseless worlds, laying waste to entire continents for the perverse glee they find in destroying a helpless foe.

The '''Fire Caste''' are near the top of the Tau’s social hierarchy.  These short-tempered and burly creatures are ostensibly the defenders of the empire, but in reality serve as the backbone of the Tau police state.  They spend much of their lives training for combat in vicious live-fire exercises that frequently result in deaths, or else spend their free time bullying the other subraces of Tau.  In combat they howl with barely-contained bloodlust, and are known for using prisoners-of-war as target practice, if they bother to take prisoners at all.

But all Tau live in constant terror of the '''Ethereal Caste''', so-named because they appear to be both everywhere and nowhere, an intangible and all-encompassing presence in Tau society.  These Tau devote their lives to preserving the order of the Tau Empire, by operating extensive surveillance networks that keep every Tau watching what they say, even when they think they’re alone.  If an Ethereal suspects a Tau of treason – or is simply feeling bored – they will order that Tau to kill himself, an order that is instantly obeyed.  A paranoid and suspicious group, the Ethereals have a grim, dark view of the universe, and believe that the Tau are surrounded by hostile aliens and beset from within by treacherous segments of their population.  They hold that there are no good actions possible in such a galaxy, and instead take the “Lesser Evil” needed for survival.  This Imperium has noted with considerable alarm that this philosophy has begun to spread through parts of its own population, driving cynics and nihilists to commit atrocities that they claim are justified by the grim(noble), dark(bright) world they live in. (Lulz, contradiction.)

'''Imperial Policy'''

For now, the Imperium has reluctantly steeled itself for war with the Tau, and has prepared its worlds on the Eastern Fringe for wave after wave of frothing Fire Warriors.  But the Emperor holds out hope that the Tau can be redeemed – indeed, one Fire Caste commander has seen the Ethereals for the manipulative tyrants they truly are and has revolted, taking a few Tau colonies with him.  This commander, named “Farsight” by his adoring troops, has opened diplomatic ties with the Imperium, and has been promised support for the inevitable counter-attack from his misguided kin.