Shown is a detail from the House of the Masks (Imperial House) family tree. Some of the following comments are best understood by referring to the fully expanded diagram.
Though brides are sometimes brought into the House of the Masks from the Great, for reasons of maintaining blood purity intermarriage is predominantly sought within the House itself. Thus the prevalence of incestuous unions: mothers marrying their sons; sisters their brothers.
Whatever his initial blood taint, a God Emperor’s blood is believed to become perfectly pure at his Apotheosis. This zero taint has a purifying effect on the blood of Their offspring. The taint is thus determined by that of the mother.
The execution of all males whose purity of blood falls close enough to that of an elected candidate, means that there are never many males in the Imperial House of high blood rank. This tends to give its women a pre-eminence in the election of God Emperors.
It is in this context that the very special favour gifted to Sardian by the God Emperor Kumatuya of his own sister, Azurea, as wife can be best understood. Among the Great, Carnelian is possessed of particularly pure blood.