You're welcome. I have spoilers from the spoiler forum.
This spoiler is about the third prince's mother
she was a priest, while she was on the front of the battlefield she helped the injured second prince and how i understood it she got used by the prince and got pregnant by him. After having the child she tried to contact the second prince but instead of helping he tried to assassinate her. She fled and found the emperor. The emperor was amused by the development and took her to the palace, protected her from his son the second prince and made her and her son his fake wife (Empress, well if you could call her that I think she wasn’t formally announced as an empress but people knew her as the mistress of the emperor I guess.) and fake son (third son of the emperor). She wants the second prince’s death because if the second prince becomes emperor she and her son would probably die by his hands immediately.
And this spoiler is about the emperor..
He uses people like a chess piece just to amuse himself he took care of her fake wife and fake son (Empress/ fake mistress and the third prince) he likes to have some drama, he wanted to watch the princes fight over the throne. He doesn’t have any kind of feelings for them at all. After the first prince (ML of course) returns he is just happy to have another chess piece to play with, he enjoyed the situation. He never cared about the first prince’s disappearance never tried to search for him at all. He is annoying, a nerve racking person
I think ceres is related to the royal family, probably a prince