So my theory is MC is the son of Qetesh, this would make him a Demi-God but bare with me here as I point out my reasoning:
•Qetesh cheated on Nergal with a mortal man, this triggered the Goblin Wars as Nergal sent his forces to destroy her followers. This happened 20 years ago, MC is 20 years old & stated to be born on the day of the Priestess cures.
•The Priestesses were cursed after Nergal's defeat into hideous old Hags so they could not fulfill their duties (Ziva was still very spry for an old woman so I dont think it took away their eternal youth but more likley forced everyone to see them for their true age) & Ziva says that when this curse happened Qetesh weaved a cure in that "only the seed of a man born on the day of the curse can lift it" but that person also could not know of their role in the cure or else it wont work. As MC was the subject this proves the above age as mentioned (sadly he cannot help any potential future priestesses because he now knows
).
•Qetesh specifically cheated with a mortal man. MC's father describes his mother as the most beautiful creature hes ever seen & that she glided towards him in the woods. MC was born not long after the end of the Goblin Wars & was left on their doorstep, to be raised by John & his wife. This again links up MC's connection to the curse & why that specific caviat exists.
•MC has immense luck with women when he wants to be charming & has great skill at getting women in his bed through charisma, deceit & impressive physicality, & manages to not only get away with alot of his shadier shit but still get the girl as well. Girls seem to instantly clock him on their radar, it's just their personality that may keep them from actually pursuing/giving in to him at first. Heck we even see this with Julia, who used to play wedding with him when they were young & obviously has taboo feelings that's she is confused/ashamed of at first.
•His ability to not only knock up women multiple times, but also for all those pregnancies to get through without a hitch. No death by pregnancy, miscarriages, or loss of life/health is also pretty impressive when you remeber this is at its core a medieval world where such things were pretty common. But MC never seems to suffer any loss with the uncountable pregnancies he has caused. If that's not a super power in it's own right I dunno what is!
•The "Ghost" (Apparition in files) is MC's mother. Notice she has the same luminous glow as the statue of Qetesh when she is happy pleased with mass? Also the glow is coming down from above... the child apparitions look just like her as well. This I think is a projection of herself that she sends forward now that she is a lil stronger but still cannot talk with her followers yet. The Ringnis made of the same metal as the Crown meaning it again has a Qeteshian connection, specifically the Crowns are used to connect the wearer WITH Qetesh, like the Ring does for MC. It would also explain why she wants the priestesses to birth his children 1) to gain a new generation of followers & 2) she wants to be a grandmother...
•His stamina & sexual prowess is also nothing to scoff at. Even without Energy potions & enhancements dude can fuck more than the average man that's for sure.
All this to say I beleive MC to be the son of Qetesh hence her interest & protection of him. This would make him a Demi-God of sex, so hes still not a super-human in the conventional way for a demi-god stud. This would explain why Nergal chose him as his "Chosen One" as well, what better way to really hurt you're ex than to use her own son against her.