Okay, so this is my attempt to clear up the plot. There's two established timelines right now. In the first timeline, Lamia becomes the duchess, and she and Aquila become close. But, she dies, and Aquila goes mad and tries to change the timeline. In this new timeline, Aquila knows that Lamia will die if she becomes duchess, so he comes up with a plan to make her become a knight instead. He ruins her brother's hand (complete douchebag move imo), knowing that with her personality, Lamia will then relinquish her title to her brother and instead become a knight.