One idea could be that the main character from Reborn is reborn into the Harry Potter world as a wizard with his unique skills. He could use his combat abilities from Reborn to face the dark wizards in the wizarding world. Another could be that a character from Harry Potter gets reborn in the Reborn universe and has to adapt to the different rules and powers there.
Perhaps a plot where the magic in the Harry Potter world combines with the special powers in Reborn. For example, the flames in Reborn could be used as a new form of magic in Hogwarts. Or a character from Reborn could be a new Defense Against the Dark Arts teacher, teaching the students his own unique fighting styles. Also, a prophecy in the Harry Potter world could be related to a character from Reborn, bringing the two universes together in a fateful way.
One idea could be that Harry is reborn into the world of 'Reborn' with his magical abilities intact. He could use magic to solve the mysteries and challenges in the 'Reborn' world, like helping Tsuna in a unique way. Another plot could involve the magic of the 'Harry Potter' universe somehow getting intertwined with the flames in 'Reborn'.
A really interesting plot could be that the reborn character is actually a huge Harry Potter fan in their previous life, so they know all the secrets and prophecies. They use this knowledge to their advantage. For instance, they might be able to figure out how to defeat Voldemort more quickly by using a combination of things they remember from the books and their own new ideas. They could also change the relationships between characters. Instead of Harry and Hermione just being friends, the reborn character could nudge them towards a romantic relationship earlier on, which would then have a ripple effect on the whole story.
Gabriel could be an exchange student from a far - flung wizarding school. He brings with him a different style of magic. Harry Potter is both curious and cautious about him. As they study together, they find out that a series of strange magical occurrences around Hogwarts are related to a curse from Gabriel's home school. Together, they try to break the curse while also learning about the cultural differences in magic, which enriches their own magical understanding.
Another plot idea is that some of the characters from Harry Potter, like Hermione, are transported to Narnia. There, they meet Aslan and learn about his world. Meanwhile, Aslan could send some of his Narnian creatures to the wizarding world to help Harry and his friends in their fight against the dark forces. This exchange of cultures and magics could create a really engaging story.
One idea could be that Peter Parker gets magically transported to the wizarding world. He could use his Spidey - sense to detect dark magic or danger in Hogwarts. Maybe he teams up with Harry Potter to stop a new villain who is using both magic and advanced technology to cause chaos.
One idea could be being reborn as Harry's long - lost twin. You could then have a whole new dynamic where you both share the burden of being the Boy Who Lived, but also have your own unique abilities and personalities. Another plot could be being reborn as a Slytherin who tries to change the house's reputation from the inside. You might start off being shunned by the other Gryffindors and friends of Harry, but slowly prove that not all Slytherins are bad.
One interesting plot could be a character reborn with memories of the future. For example, a minor character who remembers Voldemort's rise and fall and tries to change things in a different way. They might try to prevent certain deaths or change the course of the wizarding wars.
Perhaps there could be a situation where the boundaries between the wizarding world and the world of Greek gods start to break down. Harry and Percy find themselves in a strange new world that is a mix of Hogwarts and Camp Half - Blood. They must figure out how to restore the boundaries while also dealing with the internal politics of both worlds. There could be some interesting character interactions, like Hermione trying to understand the Greek mythology and Annabeth being fascinated by the magic spells.
One idea could be that Jacob, with his werewolf abilities, somehow gets transported to the wizarding world of Harry Potter. He could team up with Harry and his friends to fight against a new dark force that combines the magic of the wizarding world with some sort of werewolf - related dark magic. For example, a group of dark wizards might be trying to use werewolf blood to create a new and powerful form of dark spellcasting.
One idea could be that Harry discovers a hidden portal that leads him to the Twilight world where he meets Alice Cullen. They then team up to fight a new dark force that is threatening both their worlds.