Well, a major aspect is the impact on the overall story arc. In these fanfictions, the fight against Voldemort takes on a whole new meaning. Harry being a Horcrux means that his very existence is intertwined with Voldemort's. There's also the element of secrecy and revelation. How and when the other characters find out about Harry being a Horcrux can be a crucial part of the plot. And, of course, there's the magical mechanics of what it means to be a Horcrux. How does it affect Harry's magic? How can it be destroyed without killing Harry? These are all things that are often explored.
One popular 'Harry is Voldemort's Horcrux' fanfiction is 'The Horcrux Within'. It delves deep into how Harry's new status as a Horcrux affects his relationships with his friends, especially Hermione and Ron. It also shows his internal struggle as he tries to come to terms with this dark connection to Voldemort.
There are a lot of Harry Potter doujinshi that you can refer to:
1 Harry Potter and Defense Against the Dark Arts: This is a very popular Harry Potter fanfiction about the confrontation between Harry Potter and Voldemort in Defense Against the Dark Arts.
2 Harry Potter and the Goblet of Fire: This is another very popular Harry Potter fanfiction about the adventures of Harry Potter and Voldemort in the Goblet of Fire.
3 Harry Potter and the Prisoner of Azkaban: This is a darker Harry Potter fanfiction book that recounts Harry Potter's experiences in the Prisoner of Azkaban, including his confrontation with Voldemort.
4 Harry Potter and the Order of the Phoenix: This is another very popular Harry Potter fanfiction about Harry Potter's fight against Voldemort in the Order of the Phoenix to protect Hogwarts.
5 Harry Potter and the Half-Blood Prince: This is another heartwarming Harry Potter fanfiction about the reconciliation between Harry Potter and Voldemort in the Half-Blood Prince.
Harry could become more powerful in a way that scares his friends. Voldemort's training might focus on the Dark Arts, which are powerful but dangerous. This could change Harry's magic style. He may become more solitary as his new skills and knowledge set him apart from his Hogwarts friends who follow a more traditional path of magic.
If Harry Potter makes a Horcrux in fanfiction, it would be a major departure from his character. Horcruxes are dark magic, and Harry is firmly on the side of good. One consequence could be that he starts to be corrupted by the dark magic within the Horcrux. His friends might turn against him as they see him slipping into darkness. He could also lose his connection to the positive magic that has always defined him, like his ability to use the Patronus charm.
The story would change drastically. Harry's relationships would be different. Hermione and Ron might not be able to trust him anymore. The story would likely take on a darker tone as Harry delved into the world of dark magic. Instead of being the hero fighting against Voldemort's Horcruxes, he would now be a maker of one, blurring the lines between good and evil.
Another concept could be centered around the characters' reactions when they finally locate the seventh horcrux. There could be internal struggles among the characters, like Harry having doubts about whether destroying it is the right thing to do, considering it might hold some knowledge that could be useful against Voldemort.
Well, it depends on the specific fanfiction. Some fanfiction authors might choose to take this rather radical approach and make Harry Potter into Voldemort's assassin for various reasons. Maybe they want to explore a darker side of Harry's character, or perhaps they are trying to rewrite the whole story from a completely different perspective. For example, they could be imagining a scenario where Harry has been corrupted by some dark magic and turns against Voldemort in a very unexpected and unorthodox way.
πI recommend the following two novels to you:
1. The Soul of Hogwarts-The story of Bai Zhu challenging the magical world in the world of Harry Potter, with elements of fire shadows and masked knights.
2. " Irregular Hogwarts "-The revenge story of the third generation Dark Lord Albert Stoke, the genius alchemist who created the first generation of the knight system and the instigator of the war in the wizard world.
I hope you like my recommendation.π