The Tau Empire is an expanding alien empire located near the Eastern Fringes of the Milky Way galaxy, founded by the Tau caste known as the Ethereals. The Tau have allied with several other alien races under the philosophy of the Greater Good, which aims to benefit all species. Tau society is divided into castes that each fulfill certain roles, with the Ethereals leading the others to expand the empire in pursuit of the Greater Good.

1. By: Benjamin Burdige

2. Who Are The Tau?
The Tau Empire is a rapidly expanding
alien stellar empire situated within the
Imperium of Man's Ultima Segmentum,
near the Eastern Fringes of the Milky
Way Galaxy. The Tau Empire was
founded by the Tau caste called the
Ethereals, who lead the Tau Empire in
the name of the philosophy they have
named the Greater Good. Several
intelligent alien races (the Kroot, Vespid,
Nicassar, Demiurg and even some
humans who have turned their backs on
the Imperium known as the Gue'vesa)
have allied themselves with the Tau. The
Tau Empire borders the Imperium of
Man, and lies within the reach of the
Astronomican. It has suffered many
raids from the Orks, and also seems to
lie in the path of several Tyranid splinter
fleets of Hive Fleet Kraken.

3. Tau Empire Member Races – The
Tau
.
The Tau are a young, humanoid and
technologically-advanced intelligent race
native to the Eastern Fringes of the Milky Way
Galaxy who are fighting to expand their
interstellar empire and a philosophical
concept they call the Greater Good. The Tau
claim to be a peaceful race when possible,
asking if others will join their cause
voluntarily instead of fighting. However, if
their peaceful overtures are refused, the Tau
may well decide to conquer a planet and add
it to their growing interstellar empire for the
greater good, searing the flesh from the
bones of anyone who stands against their
benign expansions. Tau society is divided
into a number of castes, each responsible for
managing a specific aspect of their society.
The Tau's central motivating ideal is that
everyone in their empire regardless of their
species will work for the collective
betterment of everyone else, an almost
mystical philosophy they call the Greater
Good.

4. Tau Empire Member Races – The
Kroot
The Kroot are a species of savage humanoids who
are a member species of the Tau Empire who
evolved from avian creatures. Kroot are tall aliens
(a good half-meter taller than most humans), their
avian ancestry giving them a bird-like beak and long
quills protruding from their heads like hair. Smaller
quills, possibly the evolutionary remnants of
feathers, can be found scattered over their bodies.
A unique feature of the Kroot is that they evolve by
selecting traits of their defeated foes to absorb by
eating them. Due to this, the many Kroot warbands
across the galaxy often look radically different.
Kroot leaders are known as Shapers; they are
generally the Kroot with the best ability for
recognizing desirable traits in defeated foes and tell
his Kindred (the word for a Kroot clan) what to eat
to suit the task at hand. For instance, a Shaper who
wants his Kroot to gain muscle mass will take on
campaigns against Orks to acquire the right DNA,
while extensive feeding on flying predators will allow
the Kroot to grow wings. This eating of their foes
ties in with the religious beliefs of the Kroot: they
believe that when a warrior of any race dies, his
warrior spirit should be kept, and the only way to do
this is by eating his flesh. The Kroot practice this in
their "burial" customs, in which the body of the
deceased is consumed by the kindred.

5. Tau Empire Member Races -
Terrans (Gue'vesa)
The Tau Empire hosts a growing population of humans,
known in the Tau Lexicon as Gue'vesa, who were once a
part of the Imperium of Man. Ranging from ideological
defectors who hate the brutality and corruption of the
Imperial government to captured Imperial Guardsmen
and their children who have known no other life than
that among the Tau, they have been fully incorporated
into the Empire. While the humans from recently
conquered worlds are often bitter, they do often have
Tau supporters among them from the start, and the
number of these Tau sympathisers only grows larger as
they realise the manifest economic benefits that the
advanced technology of the Tau Empire can provide. For
the most part, the Gue'vesa humans are content and
treated well, and are even allowed to continue the
worship of the God-Emperor, though the Tau Water
Caste moves subtly to discourage this religion and
replace it with the Greater Good. There have also been
reports that the Tau have begun to take a tougher line
against some human colony worlds, sterilising their
populations so that the human population will die out
and leave the worlds open for full Tau colonisation. This
policy was known to have been carried out following the
Tau conquest of the desert mining world of Taros.
Whether this represents a new Tau policy towards all
humans or just a Tau desire to reserve the resources of
their conquests for their own people, these actions will
not be tolerated by the Imperium of Man.

6. The Greater Good
The Greater Good, or Tau'va (literally the "Good Greater" in the Tau Lexicon language), is the
founding religio-philosophical principle of modern Tau society which holds that all sentient beings
should strive to ensure the greatest good for the greatest number of beings in the galaxy. The
Tau'va is based on the Tau caste system and is designed to allow for the advancement of the entire
Tau society towards a more successful, prosperous and peaceful existence in the future without
much of the violent conflict that marked earlier Tau history. The Greater Good was first introduced
to the Tau during the Mont'au ("Death Age"), the long period of civil war fought between the
different Tau cities and clans on their homeworld of T'au before the formation of the unified Tau
Empire under the guidance of the Ethereal caste. It was during this time that the first Ethereals
came to the other Tau and united the Tau tribes with the philosophy of the Greater Good. This
concept involves the pursuit of perfect societal harmony and combines the particular strengths of
each Tau caste to counter the many weaknesses and divisions their culture once possessed. Within
only a few years after the Ethereals first revealed themselves, Tau culture was dominated by the
pursuit of the Greater Good and the Tau Empire began its long march towards the development of
advanced, starfaring technology. The philosophy of the Greater Good now guides the Tau in their
attempts to conquer the rest of the galaxy and unite all the intellignt races in pursuit of the Greater
Good. The philosophy forces the Tau to both desire to expand their empire for the Greater Good,
and to absorb other intelligent races and their cultures into their own, which could ultimately have
disastrous effects upon their ability to actually keep their newborn interstellar empire united. The
ideal of the Greater Good appeals to some of the other intelligent races of the galaxy, and stranded
units of the Imperial Guard are said to have surrendered themselves to the Tau and now live in the
Tau Empire, where humans are known as the Gue'vesa. Such people are considered traitors and
heretics by the Imperium of Man. During any conflict against other intelligent species, Tau
Commanders often urge the enemy leaders to stop resisting the Tau Empire since they will be
allowed to retain their own individual faiths and philosophical beliefs as long as they are
compatible with the Greater Good.

7. The Tau Ethereal Caste
The Ethereal Caste of the Tau, known as the Aun
in the Tau Lexicon, are the ruling caste of Tau
society and direct the other four castes in their
pursuit of the Greater Good of the Tau race. They
are the ultimate rulers of the Tau Empire, which is
led by a council of the wisest Ethereals. The
Ethereals guide the Tau race as a whole to work
for the Greater Good of them all and their allied
races in the Tau Empire. Their power over their
fellow Tau is such that were an Ethereal to tell a
Tau to die, the Tau would do so quickly and gladly.
The Imperium of Man would give much to learn
the secret of the Ethereals' power to command
their fellows. Ethereal Caste members are
occasionally seen on the battlefield, however
whether they are leading or observing is unclear.
The Ethereals were first encountered by the Tau
when the Tau were in an age of turmoil towards
the end of the 37th Millennium. It was the
Ethereals who ended the infighting between the
Tau cities and tribes on ancient T'au and united
them in pursuit of the Greater Good. It is always
thought that the Ethereals control the other
Castes by emitting certain pheromones. Not much
is known about the Ethereals but what is known is
that Ethereals are at the top of the command
structure of the Tau Empire. It is for the Ethereals
to decide who is worthy enough to be absorbed
into the Tau Empire.

8. The Tau Fire Caste
The Fire Caste are the military caste of the Tau
Empire. The Tau of this caste are tall and have
relatively stronger and more muscular frames than
their counterparts in the other Tau castes. This
comes from the Fire Caste's origin on the plains of
T'au, the Tau homeworld, where they were
predators and warriors. Ranks within the Fire Caste
are determined by a rite of passage known as a Trial
by Fire, which can be anything from a gladiatorial
combat to superior performance in a real battle. The
first Trial by Fire can be undertaken after a Tau
warrior of the Fire Caste has served for 4 Terran
years of active combat duty. If the Shas'la survives
his first Trial by Fire, he is promoted to the rank of
Shas'ui, or Veteran. For every consecutive four
Terran years of service thereafter, the Fire Warrior
undergoes another Trial by Fire.
The higher one's rank within the Fire Caste, the
more likely one is to be selected and trained to
become a Tau Battlesuit pilot. Upon attaining the
rank of Shas'o, a member of the Fire Caste may be
allowed to retire peacefully, although more often
than not he or she will become an advisor to the
Tau military's high command, the Shas'ar'tol. Other
than death, this is the only way to honourably leave
active service in the Tau military caste.

9. The Tau Water Caste
The Tau Water Caste is made up of merchants,
diplomats, and administrators. They are responsible
for maintaining effective interaction between the
castes, as well as communicating with and
supervising the integration of alien species into the
Tau Empire. Members of the Water Caste tend to be
taller and more slender than other Tau, and their
features are softer and more expressive. Water
caste Tau will frequently adopt mannerisms and
cultural habits of the races they deal with, although
this is often done to promote communication with
other races.
Water Caste members are bureaucrats, politicians,
negotiators and administrators. They are the
merchants and diplomats of the Tau Empire,
moving in and around the other castes to ensure
that Tau society functions smoothly, always in the
service of the Greater Good. Water Caste members
often accompany Tau expeditionary forces to
negotiate safe conduct through alien star systems
and smooth the passage of Tau merchants and
colonists. Servants of the Imperium of Man should
be aware that these Tau are exceptionally skilled at
manipulating weak-willed individuals and every
remark addressed to a member of the Water Caste
must be carefully considered and phrased to
prevent any sensitive information being divulged.

10. The Tau Earth Caste
The Tau Earth Caste is primarily made up of
farmers, laborers, and technicians;
responsible for building the machines,
cultivating the food, and erecting the
dwellings that allow the Tau to survive. The
Earth Caste also includes artisans, scientists,
and engineers. The Tau of the Earth Caste are
stouter of build than the normal Tau
phenotype, and tend to have calloused hands
and a pragmatic outlook on life.

11. The Tau Air Caste
The Air Caste of the Tau traditionally
functioned as messengers, but now fill the
ranks of the Tau Navy (the Kor'vattra), working
as pilots and starship crews. The Air Caste
lives almost entirely off-world, and due to their
constant exposure to zero and low-gravity
environments have developed long, slender
limbs, and hollow bones and so possess a
skeletal and muscular structure of reduced
strength. Prior to the unification of the Tau
castes, during the time of the Mont'au, the Air
Caste were said to possess membranous
wings, allowing them to glide on warm air
currents. The Tau use the titular prefix of
"Kor" to designate someone of the Air Caste.
They are amongst the least encountered of the
Tau castes by outsiders, presumably because
of their reduced muscle mass and duties
within the merchant and military fleets of the
Tau Empire, unlike the Water and Fire Castes'
members who more often operate outside of
the borders of the empire. Tau pilots tend to
be superior compared to their human
counterparts because they have a better depth
perception and higher acceleration-tolerance,
but lack real combat experience compared to
the best Imperial fighter-pilots.