I can actually field that.
The overall shtick is that his parents were the guardians of one of Andros's (God of Smiting/Childcare) Orphanages on a prime world. I don't know if I ever specified which, but you get the basic jist. They had a Scarlet Witch/Vision style romance, and after they fell defending said orphanage against a horde of the undead, they were taken into the realm of their god and there granted a son born of divine magic. (Classic Miracle, just as Issac)
I reverse engineered the personality of Alexander Anderson (From Hellsing) and tried to create an environment and genetic combination that would make the resulting personality a rational progression.
In many ways, I liked justiposing the uplifting (Divine reward, Heaven) with the mad (Raised by the Dead, Unnatural, and Surrounded by an endless battle that everyone is enjoying and no one takes too seriously). In a very real way, Toras isn't conventionally sane but he comes by it honestly.