Nina is the Pope's sister (he hasn't appeared yet) and she is the real saintess while sera(?) Is the fake one. In the OG story Nina is close to the "saintess" and takes back her powers from her so the King and Pope and the rest of the guys think she is a substitute for the saintess and that if she continues to live she will steal all of sera(?)'s (forgot the saint's name so just gonna call her sera) powers which means sera will die so they decide to kill Nina cuz they love Sera and Bearto is the only one that remembers her and feels had one day the Pope rushes over to Iberia to the tower where Nina was imprisoned before dying and cries bc he finds out she was his younger sis and he basically ordered to kill her. In this time line Sera loses her powers and goes travelling with the pope and the king and nina get together.theres more to that and the OG timeline is so sad for Nina when u read about it but this is the basic gist of it.