After reading the utterly strict and almost brainwashed ways of the Tau under the Ethereals... I had to wonder... could some sect of Fire caste rebel against the Ethereals? The fluff seems impossible... at first glance. But what if they came across some powerful Chaos artifact, perhaps one that both broke the hold Ethereals have on these Tau warriors and also seduced them to the power of some Chaos god... not to say they gain Chaos powers, but align themselves with Chaos nonetheless. I'm not even gonna write the fluff up before I hear at least ONE person say it's not completely and utterly impossible/ridiculous. Gotta confirm I'm not crazy and whatnot.