From the introduction: It was an age of darkness before the Ethereals came. Tau fought tau. Amid the war life was brutal and short. Disease, famine, violence - they were everywhere. Until the Ethereals came. It was they who united the disparate Tau and forged them into a people unified by purpose; the Greater Good. War faded to an unpleasant memory as society blossomed, and technology rose with it. It gave the Tau their world, banishing disease, famine, and fear a like. Soon the Tau’s reach extended to the stars.