For some reason I can't recall what the Abyssal Heritor feats do. That was something from Elder Evils, wasn't it?
Regardless, how's this for a background so far:
Regema and [brother] are the children of a nobleman that ruled over a small territory on the fringes of Marleath. Regema was born first to a human mother that was one of [father]'s concubines, who has since been made into a zombie, and then his half-brother [brother] was born to a travelling half-fiend that bewitched the father. The plan of [brother's mother] was to position a son as an heir to a noble and then slay him, making her the de-facto ruler of his manor until her son came of age (and still very influential afterwards). That plan failed, however, when the power of [brother]'s demonic blood shattered his sanity and he was found unfit to rule by the local clergy. As a result, [brother's mother] settled for looting the coffers of the manor and moving on to the next noble house. After learning that [father] was broke, the clergy revolted, killing the father and ousting the sons. Years later, the sons have expanded their knowledge of ritual magic and are now seeking a chance to re-assert themselves as influential powers in Marleath and the world.