Ok re reading this again, I've come to the conclusion that several 100 years have passed but Marianne the founder of the kingdom might have used some type of magic to keep herself alive and young. This is only a theory though. I also have the theory that in order to stay young and alive the curse that's passed down through generations is nothing more than a spell that sucks the life and power out of the person and transfers it to the person who casted it. I say this only because the scene where the king is shown at the banquet hall to welcome the new great saintess looks like a shell of a man. Whose life looks it's slowly being drained from him. Also the dark skinned noble (can't remember his name) if you look at the flashbacks looks like he was a mercenary or just some village person. I think she ended up making a deal with him or placed him under a curse as well, and then bumping him up to nobility. So that way she always has someone on her side.