Perhaps in a post - war scenario, the wizarding world is in chaos and rebuilding. Harry and Lucius, through a series of unexpected events, find themselves married. Their marriage could be a catalyst for change in the wizarding society as they bring together different ideologies. Harry might try to reform Lucius, and Lucius could introduce Harry to the more complex and often overlooked aspects of pure - blood wizarding traditions in a positive way.
One possible storyline could be that they are forced into a marriage due to some dark magic spell or a political maneuver in the wizarding world. They then have to navigate their new relationship while dealing with the shock and opposition from their friends and family.
Sure, in the realm of fanfiction, the sky's the limit when it comes to pairings. The concept of Harry married to Lucius could be part of a fanfic that aims to rewrite the entire 'Harry Potter' world from a different perspective. Maybe it's a story where the lines between good and evil are blurred, and their relationship is a key element in exploring new magical politics, family dynamics, or even a new form of magic that emerges from their union.
One possible storyline is that Draco rebels against Lucius. Draco, having witnessed the horrors of the wizarding war and the mistakes his father made, decides to turn his back on Lucius's pure - blood supremacist views. He might start to associate with more liberal - minded wizards and witches, causing a rift in their relationship.
Another idea is that Hermione gets influenced by a dark magic book that she thought was just a regular old magic theory book. The book slowly plants ideas in her head that Harry's power is too dangerous and must be curbed. As a result, she might start to use hexes on Harry in a misguided attempt to keep the peace at Hogwarts.
It's hard to say for certain. The Harry Potter fanfiction community is vast and diverse. Some writers like to create alternative universes where characters have completely different relationships. But given the nature of Harry and Lucius in the original series - one being the hero and the other a Death Eater - making them brothers would require a great deal of imagination and explanation. The writer would need to explore how this new relationship would affect the plot, the other characters, and the overall themes of the story. It might also change the way we view the magical world's social and political structures as they are presented in the books.
A possible need for Lucius in fanfiction is to preserve the pure - blood ideology. He was a strong believer in pure - blood supremacy in the original series. So in fanfictions, he might be trying to spread this ideology further, perhaps by influencing the Ministry of Magic or starting some sort of pure - blood movement. He could also need to maintain his social connections. The Malfoy family was well - connected, and he would want to keep those relationships intact for his family's sake.
Maybe Lucius wants to use Harry for his own gain. Harry is a famous figure in the wizarding world, and Lucius could be thinking of leveraging Harry's status for something, like getting back into the good graces of the wizarding society after his fall from grace.
One possible storyline could be a female Harry Potter having to work with Lucius Malfoy in a situation where they have to put aside their differences. For example, in a magical crisis that threatens the entire wizarding world. Maybe they start off distrusting each other but gradually come to respect one another as they realize they both have unique skills and knowledge that can help solve the problem.
Another storyline could be that Harry is alone as he tries to break a curse that has been placed on him during the Goblet of Fire events. The curse is making him see things that aren't there and is slowly draining his magic. Since he doesn't know who to trust, he tries to find a cure by himself. He travels to different parts of Hogwarts and even outside the school grounds in search of answers, all while feeling the loneliness of being on his own.
One possible storyline could be that she has to hide her pregnancy from her enemies who would use it against her. Another could be that she discovers new magical powers related to her pregnancy.
One possible storyline could be Harry's struggle to accept his elven heritage. He might initially be confused or even ashamed, but then come to embrace it. Another could be that his elven side gives him unique magical abilities that help him in his battles against Voldemort. For example, he could have enhanced senses or a natural affinity for certain types of magic.