One idea could be a story where Bellatrix and Narcissa are forced to work with Harry Potter due to some dark magic that binds them, and a lemon tree (represented by 'lemon' in a symbolic way perhaps) holds the key to breaking the spell. Another could be a tale set in an alternate universe where they all have to protect a magical lemon that has the power to save the wizarding world.
Well, perhaps a plot where Harry Potter discovers a hidden prophecy that involves Bellatrix, Narcissa and a lemon - like the lemon is a magical object that was once owned by their family and holds secrets about the past and future of the wizarding world. So, Harry has to team up with the two witches to uncover the truth about the lemon and the prophecy.
A possible plot could be that Narcissa has been secretly growing a magical lemon in her garden, and it has some special properties that Bellatrix wants to use for her own dark purposes. Harry Potter somehow gets involved in this situation, either to protect the lemon or to use it to his advantage against the two sisters. Maybe the lemon has the power to nullify dark magic, and that's why it's so important.
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, a plot could involve Harry being raised by Narcissa Black in a world where the wizarding world is more divided than ever. Harry, influenced by Narcissa, has a different view on blood purity. He could be trained in dark arts defenses in a more Slytherin - like way. This would make his battles against Voldemort very different. He might also have a closer relationship with Draco from the start, and they could end up as allies rather than rivals. Plus, Narcissa's influence could lead Harry to have a more nuanced understanding of the Death Eaters, which would add a lot of complexity to the story.
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.
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.
A fanfiction that focuses on a parallel universe where Bellatrix Black was not a Death Eater. In this story, she could be a mentor to Harry Potter, teaching him some unique magic skills that she has, and they could form an unlikely alliance against other dark forces. It would be interesting to see how their personalities would interact in such a different scenario.
One idea could be that Harry discovers Narcissa has a secret mission to undermine Voldemort from within. Maybe she's been secretly helping the Order of the Phoenix all along and Harry stumbles upon this knowledge.
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.
One common theme is loyalty. Bellatrix's loyalty to Voldemort and Narcissa's more complex loyalty to her family and sometimes self - preservation create interesting dynamics. For example, in many fanfictions, Narcissa will try to protect her family from Bellatrix's more extreme actions.
Well, perhaps there's a magical accident that causes Bellatrix and little Harry to be stuck in a time - loop or a magically sealed room together. At first, Bellatrix is enraged and wants to kill Harry immediately. But as time passes, she starts to notice Harry's courage and tenacity, which reminds her of the qualities she once admired in herself or others. Harry, in turn, tries to find a way to escape while also trying to figure out how to use Bellatrix's internal conflict to his advantage.