The world is populated by people. Hundreds, thousands, millions of people. Of those people, there tend to be the noble families that rise up and rule the ‘common’ person. However, of those noble families, there is a breed that rises up and above even the other nobles. These are the Hereditas, those who have the Blood of Divinity.
The ways of becoming Hereditas are as various as those divinities that bestow their essence upon mortals.
In some cases, a deity will kick the can, and a mortal will be nearby. The strength of divine essence is such that it overwhelms the human physiology, inundating the very essence of someone’s being. The results vary wildly, due to the nature of divinities, but one thing is always the same: the person is no longer merely mortal. They have been changed into something more.
In other cases, a mortal will be seduced and impregnated. While that person will not gain divine essence and become Hereditas, their child will be, for that child has the blood of divinity flowing through their veins.
In even rarer cases, a deity will bestow the mantle of power upon the devoutest of devout, making them more than they are. Quite often when their children are born, they also are Hereditas.
Regardless of how it happens, those who become Hereditas are more than mortal. Sometimes their appearance changes, becoming more and more like that deity that they gained their essence from. On other occasions, they become stronger, faster, or gain special abilities related to that deity.
This change is what allows them to rise above the rest of the world, including nobles. Because they have divine essence within them, they are more capable than others at ruling. More than one monarchy has been overthrown thanks to a rebellion with a Hereditas at it’s head.
This is meant to be something of a special bit of flavor that you can add to both characters, or NPCs to make them more interesting. The exact rulings on how Hereditas come about and what advantages (or disadvantages) they gain from having divine blood is by nature tied closely to a game world. However, a large chunk of classical fantasy has included divine blood at some point or another, so this sort of character-flavor isn’t out of line.