The sex slave is completely at the mercy of his or her master. Everything the master gives them is pleasurable, and obedience to the master is a source of happiness. The sex slaves will continue to be used by their masters until they are destroyed, but with the Blessing of BE, Stille will never be destroyed and will forever be loved by the bosses as a sexual outlet and impregnation pouch. There is no magic or potion that can lift the sexual enslavement. (The master can appoint a successor, and even if all the masters die, they will do anything to get a new master.)
Boss larvae.
They hatch and grow inside the mother's body, absorbing bodily fluids and magical powers. When they reach a certain size, they begin to rampage inside the body and prepare to give birth. After confirming this, the adult boss takes action to promote the birth of the mother. The larvae are male only, and there seems to be another egg-laying method to produce females.