The Lords of Hell have vowed to bring the mortal world under their physical dominion and the result is a slow burning apocalypse of war, fire and death.
They gained an initial foothold in the south of the planet’s continent at a place called Halendorf, now known as Hellmouth, then their forces overwhelmed and overran the kingdom in which Halendorf sat. Demonic generals and captains directed and drove lesser fiends across the landscape, adding human soldiers to their forces as they went. After a generation they produced a new abomination, the demonspawn. Sired by high ranking demons on human women, the powers they inherited from their fathers were coupled with a greater understanding of humans than those fiends were capable of possessing and they joined the ranks of Hell’s greatest generals and spies.
Faced with foes of mixed human and demonic blood, the embattled humans prayed to their gods for assistance. The answer to those prayers was the godssons, demigods born of mortal women. The gods would only act on receipt of a petition from the mother to be and so the Rite came into being, regulated by their priesthoods and with some variation for individual gods. Although it is treated as a solemn ritual, in fact the initial part is a supplicatory prayer and most of the rest is to satisfy the participants that the supplicant is human, and not a demon or demonspawn, and that the responder is, indeed, a god. Occasionally the god that the supplication is made to is not the god who responds, resulting in confusion and sometimes introducing the influence of a previously unworshipped god.
Needless to say, persons of unconfirmed bloodline who exhibit powers and abilities beyond the human norm are regarded with suspicion by the general population and authorities alike.