if anyone could help me i would be very grateful i have been trying to remember this book for years it is part of a series the books plot goes like this

At the start of the book he good guys who are vampires are hunting the bad guys who are vampires as well but of a crazy kind where if they turn someone they go crazy and have to be put down they get there just after the bad guys turned a woman and cant remember if they kill the bad guys or if they bad guys ran off but the main character saw something in the woman and decides to try to save her

The main male character it turns out is the first vampire i also remember he is a demigod who's mother is Nyx the goddess of darkness

later in the story the woman gets kidnaped and chained outside of a building just before daybreak and when the mc finds her is unable to get the chains off before daybreak and has to shield her with his body while being taunted by Apollo and while the sun cant kill him it hurts him and makes him very weak and his mother has to come and give him ambrosia which she is not supposed to give him very offen for some reason i cant remember but he feeds to the girl because while he shielded her she still got hurt and after he finishes giveing it all to the girl his mother comes back and gives him some more but makes him eat it and not give more to the girl

other small details i can remember is the mc lives in a cave that can only be entered by turning to mist