From the introduction:
Your family has a terrible secret. Your wealth and power is made possible by a deal your bloodline made with The Beast - an utterly inhuman entity. Every generation, one member of the family must carry the Beast’s spawn. You have been selected by your family as one of the potential mates for the Beast. There were other members of your family who could have done this, but they were not selected, and you were. To carry the Beast’s spawn destroys you utterly - you will not die but you will be transformed both physically and mentally and become something abominable to your current perspective. If any one of you were to refuse the responsibility of being one of the chosen, you would be disowned and cut off from all of your family’s resources and risk bringing down the wrath of the Beast and the destruction of your entire family.