If Harry Potter were raised by Narcissa in fanfiction, it would change his entire world view. Narcissa is a complex character. She's loyal to her family and the Dark Lord to an extent. Harry would likely be taught magic in a more traditional pure - blood way. His appearance might be different too, as Narcissa would probably ensure he was dressed and groomed in a more sophisticated manner. Also, his understanding of the wizarding world's social hierarchy would be shaped by Narcissa's beliefs.
Harry's personality would be greatly influenced. He would be more polished in his behavior, as Narcissa would demand propriety. He might be less likely to take risks without thinking, as Narcissa would have instilled in him a sense of caution. His sense of loyalty would be more complex. Instead of the straightforward loyalty he has in the original story, it could be divided between Narcissa's family values and his own sense of right and wrong. Also, he may have a more aristocratic air about him, with a refined way of speaking and interacting with others.
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.
Harry's personality would change significantly. Narcissa's influence would make him more secretive. He would learn to keep his cards close to his chest. Instead of being the open - hearted hero we know, he'd be more of a behind - the - scenes operator. His relationship with authority figures would also be different. He wouldn't be as quick to trust Dumbledore or other adults. He'd have a more cynical view of the wizarding world's power structures. His social skills would be more attuned to the Slytherin way of networking and manipulation, though he would still have his core of goodness that would lead him to oppose Voldemort in a different, more strategic way.
One great 'Harry Potter Narcissa fanfiction' is 'The Redemption of Narcissa Malfoy'. It shows a different side of Narcissa, exploring her inner thoughts and her journey after the war. It's a very character - driven story that gives Narcissa more depth than what we see in the original books.
I'm not sure if there is a specific fanfiction with such a plot. Fanfiction covers a wide range of themes and ideas, but this one seems rather unorthodox and might not be very common. There are many fanfiction platforms out there, but it's difficult to say for sure without a thorough search.
One possible story could be where Harry Potter, through some magical twist, finds himself in an unexpected situation with Narcissa in a harem - like setting. Maybe it starts with a spell gone wrong during one of his adventures that transports him to a hidden realm where Narcissa is part of a group that he has some sort of connection with. The story could then explore their relationship, how Harry adapts to this new and strange situation, and the dynamics within the harem.
One reason could be the large fan base of Harry Potter. Fans are more likely to write about him in relation to other characters like Narcissa. Since Harry has so many different aspects to his character, such as his courage and his mysterious connection to Voldemort, it gives a lot of room for creativity when paired with Narcissa. He can be the hero who changes Narcissa's view, or he could be in a conflict with her, which makes for engaging fanfiction.
Family loyalty is also a big theme. Narcissa is deeply tied to her family, and fanfictions often play with the conflict between her loyalty to her family (like Lucius and Draco) and her possible newfound understanding or connection with Harry. It creates a lot of internal and external drama.
In many Harry Potter fanfictions, Narcissa is often portrayed as a complex character. Sometimes she is shown as a mother who is desperate to protect her son, Draco. This is in line with her actions in the original series where she lied to Voldemort about Harry being dead to save Draco.