
What did the emperor do to Rieta's family that caused such severe grief for her? I can't recall the story and I don't want to go scrolling through 160 chaps to find out

The emperor’s brother who had divine powers and high authority accused Rieta’s mother being a witch or using black magic to subjugate the demons. He killed the Beatrice ( Rieta’s mother ) without the kings permission and Beatrice’s mother grieved of such loss of her daughter and cursed the emperor. Beatrice was sent to the emperor’s kingdom to form peace but the brother of the emperor had seen the subjugated demons with Beatrice and accused her of using black magic and burned her. Beatrice and the emperor hadn’t met as the emperor was away and the brother took the decision upon himself to burn Beatrice. Beatrice’s mother was angry and cursed the emperor with her life , as all she did was send her daughter to form peace but she was accused and killed instead.
I have the gist of the plot but on a whole there are some flaws in the story telling which make it hard to follow along, especially as a story which really started as a what seemed like a PWP. That is to say, it wasn't plot heavy to begin with, and in fact the magic spell on Leah feels like a cop out to drag on the series; it feels unexpected, but not in an exciting way.
I feel like it needs more context.
Also, the art is kinda.... Weird. It gives me that uncanny valley vibes, and the expressions the characters have are unnerving.
The novel goes into more detail about it, although the manhwa is following the flow its just lacking about details so i think you need to read to novel if you really want to grasp the whole story and actually understand it.