From what i can understand of the Raw's.. The Duke forces Fl to learn the vital parts of the body everynight.. aka having her stab corpese..
He wants Fl in dispair and isolated from the world.. "teaching" her not to trust anyone..
This included by having one of the maids Fl gets close to chose between him killing her or FL.. and the maid beggs fl to die/ take the punishment for her.. destroying the peace and friendship that gave Fl a sense of stability... He then tells her to never trust anyone.
Fl continues her "training in killing" and her daily maid work, but is absent from breakfast because she is her washing her hands for the blood she still smells on them. She comments that no matter how much she washes them, the smell wont come off.
During normal work fl looks pale and coughs up blood, that night sick in bed she contemplates passing away.. The Duke apears in a bright light and says she cant die, he kisses / using mouth to mouth to get her to drink a light blue liquid that heals her and she falls a sleep.
The next day he acts like nothing happened..Later one night Fl sneaks into the Duke's chambers and tries to stab the Duke using the skills he had her learn. The Duke coments that he is proud of her for her skills yet unhappy that she went for him.
He prety much tells her she has no where to go, her life is in his hands and she has noone cause everyone can turne on her so she best be a good dog..
Fl inraged screams that he Ruined her life and that she is sick of playing to his whim.. and tries to stab him. He takes her dagger and says she should know how to use a real weapon, giving her his rapier and telling her to try again while smiling / laughting.
Fl says F this and tries to stab herself, the Duke grabs the rapier before Fl can stab herself (causing blood to flow from his hand) and looks at her paniced and flustered saying he wont let her kill herself.
This catches Fl off guard (the psyco wants her to live), she laughs at him and caughs up alot of blood and the Duke kisses her again forcing lightblue liquid down her throat.
As Fl heals she asks WHY!, the Duke says he will not let her die no matter what and he will never let her go either... Fl loses everything and starts to feel nothing for her coworkers and follows orders and dosnt bother to question anymore.
Im skipping some minor stuff here.
The Duke meets the Prophet who he seems close to.
The prophet is a young woman with blue eyes, dark blonde hair with set curls. The prophet takes a glimps at Fl and stops smiling.
The Prophet gets in her carriage with the Duke.
From what i could guess, she asks him how its going with his "Destined One" aka FL. The Duke becomes unhappy and says to mind her own buisness.
The prophet meets the prince and other oppl and later is almost assasinated in her chambers, but is saved by one of the Duke's ppl who tell her to Do her Job.
Later while laying in bed with a big book the Prophet thinks of Fl, while showing as sad face/ expression (feeling sorry for Fl). She seems to know Fl's future..
Just my speculation..
The Duke seems to be able to use magic.. and views "Other worlders" as a danger to his "Plans".
He has been using the Prophet to find and murder the "Other worlders" because their actions have affected events of his world... this includes him meeting Fl.. who seems to be either his "Soulmate... or Bound to him in som way"... He wants FL to trust noone, know how to kill and never think of leaving him.. yet he wont let her die and seems to want her to be as broken as he himself is.
The more pain and discorce Fl feels the "happier" the Duke seems to be.. Either he is training her to survive or he is just a psycho.