One plot idea could be a magical accident that causes Hermione to take on Bellatrix's appearance. She then has to deal with the reactions of her friends and foes alike. For example, the Death Eaters might mistake her for Bellatrix at first and she could use this to her advantage to gather information. Another idea is that it's a curse placed on her by a dark wizard who wants to cause chaos in the wizarding world. Hermione would then have to find a way to break the curse while looking like Bellatrix.
Another plot could involve Hermione using her intelligence to uncover secrets within Bellatrix's family history that have been hidden for generations. This could lead to a strange alliance between them as they both seek the truth. For example, Hermione might find out that there was a powerful magic in Bellatrix's family that could be used to defeat a new dark force emerging in the wizarding world.
A plot could involve the daughter using her unique position to bring about peace. Since she has a connection to both the 'good' side through Hermione and the 'dark' side via Bellatrix, she could be the key to bridging the gap between the two warring factions. For example, she might use her knowledge of both sides' secrets to negotiate a truce.
A plot could involve Hermione and Bellatrix both being Animagus and their forms having some sort of connection. For example, Hermione's Animagus form is a small, intelligent animal like an owl, while Bellatrix's was a large, powerful but dangerous bird like a raven. They unknowingly cross paths in their Animagus forms and some sort of magical bond or understanding starts to form between them. This could lead to a complex relationship where Hermione tries to use this connection to stop Bellatrix's evil deeds.
A plot could be about Hermione and Bellatrix having to work together to solve a mystery within the wizarding world. Maybe there's a dark magic object that is causing chaos, and their combined knowledge of magic, despite their differences, is needed to stop it.
One idea could be the forced marriage leading to a power struggle within the Death Eater ranks. Hermione, with her intelligence, might try to outwit Bellatrix and use the situation to gather intelligence for the Order. For example, she could pretend to be compliant while secretly passing on information.
One idea could be a time - travel plot where Hermione somehow gets sent back in time and has to deal with a younger Bellatrix. Maybe she tries to change Bellatrix's path to the dark side. Another could be a magical duel between Hermione and Bellatrix where Harry is caught in the middle, forced to choose which side to help. Or a plot where Bellatrix, under some sort of spell, has to team up with Hermione and Harry to fight a greater evil.
One plot idea could be that Bellatrix, in an alternate reality, has a change of heart and decides to protect Hermione from other dark forces. Maybe she sees a bit of herself in Hermione's fierce determination. Another could be that Hermione, while researching dark magic for a school project, accidentally stumbles upon a long - forgotten connection between her family and Bellatrix's, leading to a strange alliance. And a third idea might be that Bellatrix is cursed and Hermione is the only one who can break the curse, but in the process, they have to face their deep - seated prejudices about each other.
One idea could be that Harry's new appearance as a girl causes a stir at Hogwarts. His friends are initially shocked but then accept him as always. Another could be that he uses this new look to his advantage when it comes to spying on the Death Eaters, as they don't recognize him. Maybe he even gets to experience the wizarding world from a different perspective as a girl, like how people interact with him differently in social situations.
One idea could be that Harry discovers a hidden side of Bellatrix where she has a group of followers who are all intrigued by Harry's power. They form an uneasy alliance at first, but as time goes on, they start to respect and care for each other in their own strange way.
Well, in this fanfiction, perhaps there's a time - travel element. Hermione goes back in time and somehow gets involved with Bellatrix in a way that changes their relationship. Bellatrix might be less extreme in her younger days, and Hermione's modern ideas influence her. This could lead to a relationship that blossoms into marriage over time.