Yes, there might be. The Harry Potter and Final Fantasy universes are both very popular, so it's likely that some fans have combined elements from both in fanfiction. You can try searching on fanfiction websites like Archive of Our Own or FanFiction.net.
In 'Harry Potter Sephiroth fanfiction', a recurring theme is the adaptation of Sephiroth to the new environment. He has to deal with the rules, cultures, and social structures of the wizarding world. There may also be a theme of power struggle, as Sephiroth's power could either be a threat or an asset in the fight against the dark forces in the Harry Potter series. Additionally, the theme of identity can be explored, as Sephiroth may question who he is in this new and different world.
Well, one possible plot could be that Harry discovers his true father is Sephiroth. This could lead to him having new and strange powers that he has to learn to control. He might face discrimination from both the wizarding world and those who know of Sephiroth's dark past. And he would have to figure out how to use his new identity to fight against the forces of evil in the wizarding world, which could be different from the normal threats Harry usually faces.
Yes, there are some out there. You can try searching on popular fanfiction websites like FanFiction.net or Archive of Our Own. Just type in the exact phrase 'Harry Potter son of Sephiroth' in their search bars, and you'll likely find a few stories. However, the quality can vary greatly, so be prepared to sift through some not - so - great ones to find the gems.
Well, perhaps Sephiroth's reincarnation in the Harry Potter universe is a result of some ancient magic gone wrong. He is born with his signature long silver hair and a strange, otherworldly aura. As he grows up, he discovers his past life memories and decides to use his knowledge of both worlds to gain ultimate power. He might start by manipulating the Hogwarts houses and eventually aim to take over the entire wizarding world. He could form alliances with dark wizards and creatures, all while the main Harry Potter characters try to stop him.
It would be really wild. Harry would grow up with Sephiroth's strict and powerful influence. He might learn combat skills much earlier and in a very different way compared to how he was raised in the original series. His view of magic and power could be warped by Sephiroth's teachings.
It's not a typical or well - known concept. Harry Potter has its own lore and a large fan base that mainly focuses on the wizarding world's internal elements like the houses of Hogwarts, the fight against Voldemort, etc. Sephiroth, on the other hand, is a very different character with his own complex backstory in the Final Fantasy universe. Fanfiction usually tries to stay somewhat true to the source material, and melding these two would be a very odd and perhaps not very popular approach in the general fanfiction community.
Ron would probably be more wary and hostile towards Sephiroth at first. He might see Sephiroth as a threat right away, especially if Sephiroth showed any signs of aggression. Ron would rely on his Gryffindor courage to stand up to him, but his insecurities might also surface. However, as the story progresses, he could learn from Sephiroth's power and maybe even develop a grudging respect if Sephiroth had any redeeming qualities.
One idea could be a crossover where Sephiroth somehow ends up in the wizarding world of Harry Potter. Maybe he's a dark force that Voldemort tries to use for his own gain, but Sephiroth has his own agenda. He could use his powerful magic, which is different from the magic in the Potterverse, to create chaos.
Well, I haven't read all of the 'Harry Potter Sephiroth fanfiction' out there, but often the really good ones will have interesting plot twists. Maybe Sephiroth somehow ends up at Hogwarts, or there could be a conflict where the powers from the Harry Potter universe and Sephiroth's powers collide. You should also look for ones with high ratings and lots of reviews to find the best ones.