The Great Houses
The static, aristocratic bloodlines which have -traditionally- been seen as responsible for the structure of the Spiral Politic, the Houses can be considered the central power of the War Era universe. In fact the word "bloodline" might be misleading as it suggests something genetic and the Houses seem to have no real genetic status at all: as the society responsible for engineering history, they perceive themselves as being parts of the historical process much more than being a people. - The Book of The War