A cool plot might be that Bellatrix, in an alternate reality, is a good witch and she teams up with Hermione and Harry to stop an evil version of Voldemort. They could use their combined magic skills, Hermione's intelligence and Bellatrix's raw power. Another plot could be that Hermione discovers a long - lost relative who was friends with Bellatrix in their youth, and this connection leads to a complex relationship between them. Also, a story where Bellatrix's mind is trapped in Hermione's body and they have to work together to get Bellatrix's mind back to her own body while also facing various threats.
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.
Well, there could be a plot where Hermione, through some dark magic accident, starts to have visions of Bellatrix's past. This makes her understand Bellatrix better and she tries to find a way to redeem her. Another plot could be that a powerful magical object is discovered and both Hermione and Bellatrix are after it for different reasons. Harry gets involved to stop them from destroying each other. Or perhaps Bellatrix is cursed and only Hermione has the knowledge to break the curse, so they are forced to cooperate, with Harry being skeptical of the whole situation.
One idea could be a time - travel fanfiction where Hermione goes back in time and has to face Bellatrix in a magical duel. Harry could be caught in the middle, trying to protect Hermione. Maybe Bellatrix has a secret that could change the course of the wizarding war, and Hermione discovers it.
Some fanfics explore Bellatrix's family relationships more deeply. Like her relationship with Narcissa. There could be a plot where Bellatrix has to choose between loyalty to Voldemort and protecting her sister, which adds a lot of emotional depth.
Well, it could be that Fem Harry Potter is actually a long - lost relative of Bellatrix's family. Bellatrix initially hates her because of her association with Dumbledore and the Order. But as the story progresses, they find out some dark family secrets that connect them. They then have to decide whether to keep fighting against each other or team up against a greater evil, like a new dark wizard who is more powerful than Voldemort and is threatening the wizarding world.
One idea could be a time - travel plot where Harry somehow travels back in time and has to interact with Bellatrix in her younger days. This could lead to him trying to change her path before she becomes a Death Eater.
A really interesting plot could be Bellatrix being given a chance at redemption. In this fanfiction, she could start to question Voldemort's motives after seeing the destruction he causes. She might then try to secretly help the Order of the Phoenix. Also, a plot about her teaching a young Death Eater the ways of the Dark Arts and having second thoughts about it mid - way through could be fascinating.
One idea could be that Harry discovers his true parentage and has to struggle with his identity. He might be torn between the side of good that he has known all his life and the dark legacy of Bellatrix. Another plot could involve him facing discrimination from both the wizarding world that hates Bellatrix and the Death Eaters who might see him as a tool or a threat. For example, he could try to use his knowledge of Bellatrix's magic, which might be more complex and dark - tinged, to fight against Voldemort in a different way than in the original story.
One idea could be a story where Bellatrix has a moment of doubt about Voldemort's methods. Maybe she starts to see the destruction he's causing and has to decide whether to stay loyal or turn against him. And Harry Potter could somehow be involved in this internal struggle of hers, perhaps by showing her a different path through his own actions and values.
Well, a cool plot for a 'Harry Potter and Bellatrix Fanfic' might be that Bellatrix, in a moment of confusion during a battle, uses a spell that transports her and Harry to a different time period. There, they have to rely on each other to survive and in the process, Bellatrix starts to question her loyalty to Voldemort. Also, a plot where Bellatrix discovers that Harry has a hidden power that could be used to bring back someone she lost, and she bargains with him for it could be interesting.
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.
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.