So, as we saw she is very cunning and strategic, she will use any means to get what she wants, and i mean any!
First thing she does is go to her father and ask for his support. Her father is very strict and only cares about her brother who is the heir. He is very important to the King since their house is very powerful as they lead the country's "Shadow organization". She persuades him to give her some shadows for protection, and he agrees giving her "John" and a rookie "Poppy". She uses both of them as spies to find out dirt one everyone necessary, not only the capture targets.
Then we meet the other girls. All capture targets have fiances except her brother. They come to Cassandra and want to harass the Saintess for always being next to their fiances. But she stops them and asks them to leave all of it in her hands. They agree...
So her revenge begins by crushing the event where the Saintess first shows her power. She uses her father to make the people in her domain be more hygienic to stop the spread of the plague, and thanks to the shadows spreads the methods around. This method makes people doubt that the Saint is even necessary.
Then on the first party, the Saint event is to heal a poisoned noble woman, but thanks to the shadows she exchanged the drinks and made Poppy dressed as a maid spil the poisoned drink on the Saintess. The poison was actually a super aphrodisiac, which makes her flee horny from the party lol
The Saintess then becomes a shut in and the 1st Prince a laughing stock to all the nobles...
Now that the public eyes have shifted, the Queen invites Cassandra to tea. There she is informed that she and the King value her way more than the 1st Prince (
mainly because of her father), and she is asked by the Queen if she wants to switch to the 2nd Prince, that she will be made the Queen no matter what. She actually declines, stating that even tho the 2nd Prince is better and a more fitting King he already has a fiance, and she doesn't want to stand in the way of that. She tells the Queen that she will open the eyes of the 1st Prince... And this is the twist, she plans to marry the 1st Prince even tho he is scum! She wants to crush him so much that he will be just a King in name, she will be the true Ruler!
So the condemnation event is next, but before it happens she walks in the Princes office where all the capture targets are gathered (
this is the event from the 1st page we saw in this manga ch). She lays her whole plan in their face, and as they start to insult her her brother defends her. Everyone is stunned why is he taking her side, no one gets it. She actually opened his eyes in secret by stating him some facts how he will be exiled by father and what is really going on with the Saints. It shocked him so much that he switched sides instantly!
She then tells them what is really going on with the Saint. Turns out she fell in love with the handsome Gardners son and is in a physical relationship with him (
this is what made her brother disgusted and switch sides lol). Everyone is shocked but it doesn't stop there, she informs the other 3 targets that they are disinherited, and shows them the King's letters. Alexis is to be sent to the frontiers, Heinz is thrown out to be a commoner, and Rudolf is to be sent to another country. All 3 of them get dropped by their fiances as well...
The Prince still can't believe what is happening but she makes it clear that she will not abandon him, and he will still be King. This exchange actually makes him fall for her
So she does marry him, and becomes the real Ruler. Everything the Prince/King does goes trough her. She also helps the girls get fiances that actually deserve them, and she employs the Saintess and her lover in her family's domain after they eloped.
Then it ends with her saying "I am evil, and i will always be evil. I am the villainess after all."