In a fanfiction, Harry Potter could be sent to the world of Final Fantasy through some sort of magical accident. There, he meets Sephiroth. Harry, with his knowledge of good and evil from his own world, might try to prevent Sephiroth from causing more destruction. He could use his wizarding skills, like spells and charms, in the new world which would be a very interesting combination with the Final Fantasy elements.
A possible fanfiction plot could involve a prophecy that ties Harry Potter and Sephiroth together. This prophecy might be about a great battle that could save or destroy multiple worlds. Harry, with his friends from Hogwarts, and Sephiroth, with his own allies or lackeys, could be on opposite sides of this conflict. The story could explore how their different powers and personalities clash and interact throughout the events leading up to the final showdown.
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.
One great fanfiction could be about a wizard from the Harry Potter world being transported to the world of Final Fantasy 13. Maybe they have to learn the new magic system there while also trying to find a way back home. It could be full of exciting battles and new friendships.
A possible fanfiction could involve a fusion of the two worlds' power systems. The characters from both Naruto and Final Fantasy 13 could exchange knowledge about their abilities. For instance, the summonings in Naruto could be related to the Eidolons in Final Fantasy 13, and they could find ways to combine their powers for a greater good.
One idea could be to have the characters from RWBY end up in the world of Final Fantasy 15. For example, Ruby could meet Noctis and they could team up to fight some common enemy. Ruby's speed and scythe - wielding skills could be a great addition to Noctis' combat style.
Perhaps a Final Fantasy character gets transported to our modern world and has to work at a Lululemon store to earn money for their journey back home. They learn about modern fashion and the concept of athleisure, and there could be some comical moments as they try to adapt to this new environment.
One idea could be to have Naruto characters in the world of Final Fantasy 10. For example, Naruto could be a Blitzball player, using his speed and agility. Sakura could be a healer, like a White Mage in Final Fantasy 10. They could be on a quest to stop Seymour from achieving his evil plans, with Naruto's Rasengan being a powerful attack against the fiends in Spira.
One idea could be to have Naruto characters in the world of Final Fantasy 15. For example, Naruto could be a guest in Noctis' group. He could use his ninja skills like shadow clones to help in battles against the daemons in Final Fantasy 15. His chakra could be seen as a new form of magic in that world.
One interesting fanfiction could be a crossover where the magic from Harry Potter meets the high - tech world of Final Fantasy 7. For example, imagine Harry and his friends being transported to Midgar and having to deal with Shinra while also using their magic. There are likely some out there that explore how the different magic systems interact, like how materia could be related to wand magic. Another aspect could be the characters' reactions to the different cultures. Harry might be shocked by the slums in Midgar, while Cloud and his group could be intrigued by Hogwarts and its secrets.
One example could be a story where the characters from Harry Potter find themselves in the world of Final Fantasy 8. Maybe Harry uses his magic in the same way Squall uses his gunblade, creating unique battle scenarios. Another could be a crossover where the spells in Harry Potter are combined with the junction system of Final Fantasy 8, leading to some really interesting power - ups for the characters.
One idea could be that Fluttershy somehow gets transported into the Harry Potter world. Maybe she arrives at Hogwarts as a new kind of magical creature that the students have never seen before. Her gentle nature might initially cause confusion among the more rowdy students, but she could gradually make friends with the likes of Luna Lovegood, who would be intrigued by her uniqueness.
Another concept could be that Harry Potter discovers he has a connection to Magneto's mutant powers. This might happen during a strange encounter with a dark magic object that unlocks a latent power within him. He then has to learn how to control these new abilities while also dealing with the threats in his own wizarding world, and he might seek out Magneto for guidance in a secret meeting across the boundaries of their two worlds.