The Power is a religious dictatorship. Something a long the line of the Catholic Church in structure (just more ruthless and fanatical). One major point about this society is that all information and technology is under the control of the Church; pilots, technicians, programmers, librarians. All are involved with the Church at some level.
The only thing that keeps the Power in check, at least partially, is their Military. Because the Power is a religion they tend towards spiritual matters, and dont have time for the more mundane aspects of control (eg combat). Hence, there is a military arm of the Government which deals with security and combat, when necessary. The two factions, Church and Military, are allways at odds with each other. Even though the Power has more political pull, the Military has more guns, so they tend to keep each other honest. Although, the Power usually has the final say in most things.
The Power has its own Security/Military force which is independant of the Military, and is feared by most of the civilians.
There is no slavery here. When The Power finds and conquers an inhabited world they determine whether or not this new race will be a benefit to their society or a threat/hinderance. If it is determined to be a benefit the people are given the choice of submission and integration or death. Otherwise, they are simply destroyed. Once integration begins, it usually takes at least two generations before the inhabitants are allowed into the general population. This allows for reeducation of the masses into the proper order of things.
There are three distinct classes within the Power; Church, Military, and Citizen. About 80% of the poplulation is Human or Humanoid.