Aristoi

Gabriel is one of the Aristoi, the elite class that hold dominion over a glittering interstellar culture, their rule more absolute than that of any Old Earth tyrant. When another of the Aristoi is murdered, Gabriel finds that the foundations of his civilization are tottering, and that his own power may have its roots in the greatest lie in all history.

In order to defend himself and the interstellar order, Gabriel must go on a quest into the heart of barbarism and chaos, and discover within himself his own lost, tattered humanity.

Synopsis from Open Library.