They are taken at a young age, before they remember anything about their parents, selected by the ability to go through the process of becoming a Prince. The Empire is partially commanded by some 10 million Princes. The Emperor must be replaced every twenty years because after that, the Emperor is no longer able to keep from being subsumed. Until then, they rule over the Imperial Mind, which is actually the minds of the former Emperors, subsumed into the Mind till they are effectively one with it. The Empire is ruled by an Emperor who abdicates after twenty years.

These are used as a 'Trinity' by the empire to defeat their enemies the Sad-Eyes (which control beings mentally they are called Sad- Eyes because the only part of the body they cannot control are the tear ducts), though stronger in Psi-tek, have limited Bitek and Mektek, and are defeated thus the Naknuk rebels, former Imperial Princes (presumably of House Naknuk) focused entirely on Bitek, shunning the other two, as a result they are defeated the Deaders, meanwhile, never allow themselves to be captured, if they are defeated, they self destruct- at the same time, they never take prisoners. There are three 'teks', or technologies types used by the Empire Bitek, which deals with biological weaponry and technology Psitek, which deals with the mental equivalent of the former and Mektek, which deals with the Mechanical equivalent of the former two. Each of these, though, is reported to be inferior militarily to the Empire. The majority of the galaxy (presumably, though not explicitly stated, the Milky Way) is under the control of the Empire however, there are at least three other political entities stated The Naknuk rebels, the Sad-Eyes, and the Deaders. The setting is in the distant future (it is not explicitly stated). A Confusion of Princes by Garth Nix is an interesting book.

A confusion of princes