This story begins every hundred years, and it always begins the same way — with the legend awakening. [...] Every hundred years, they try to overtake our world, and we always think we've destroyed them. The legend also has it that every hundred years... we're wrong.
Thus throughout history a struggle which is the same in its main outlines recurs over and over again. For long periods the High seem to be securely in power, but sooner or later there always comes a moment when they lose either their belief in themselves or their capacity to govern efficiently, or both. They are then overthrown by the Middle, who enlist the Low on their side by pretending to them that they are fighting for liberty and justice. As soon as they have reached their objective, the Middle thrust the Low back into their old position of servitude, and themselves become the High. Presently a new Middle group splits off from one of the other groups, or from both of them, and the struggle begins over again.