Maybe Arthur Curry is sent to Hogwarts on a mission. He has to learn magic quickly to blend in and help solve a mystery that involves dark wizards trying to steal Atlantean magic. Along the way, he befriends Harry Potter and they exchange knowledge - Arthur teaches Harry about the ocean and its secrets, while Harry shows Arthur the ropes of wizardry.
One possible plot could be that Harry Potter discovers a magical portal that leads him to the underwater world of Aquaman. There, he has to learn the ways of the underwater society while also using his magic to help Aquaman fight against an evil force that threatens both the wizarding world and the underwater realm. Maybe a dark wizard has teamed up with a sea - based villain, and Harry's unique skills are needed to defeat them.
They would probably start off being a bit cautious of each other. Harry would be intrigued by Arthur's unique powers and his connection to the ocean. Arthur, on the other hand, would be curious about Harry's magic. They might exchange stories about their respective worlds at first, like Arthur telling Harry about Atlantis and Harry sharing tales of Hogwarts.
One possible plot could be that Aquaman discovers a magical portal in the depths of the ocean that leads to the wizarding world of Harry Potter. He then teams up with Harry to fight a new threat that is endangering both the underwater kingdom and Hogwarts. Maybe it's a dark magic - using sea creature that has gone berserk.
One possible plot could be that Aquaman somehow finds himself in the wizarding world of Harry Potter. Maybe a magical spell gone wrong transports him there. He could use his unique underwater abilities to help the Hogwarts students in a task related to the Black Lake, like retrieving a powerful magical artifact that has sunk to the bottom.
One idea could be that Harry Potter discovers an ancient magic artifact that transports him to the time of King Arthur. There, he uses his magic skills to help Arthur in a battle against a powerful dark sorcerer. Maybe he teaches some of the knights a few new spells.
One possible plot could be that Percy Jackson, being a son of Poseidon, discovers a connection to Aquaman's underwater kingdom. Maybe there's a threat to both the demigod and Atlantean worlds, like an ancient sea monster awakened by dark magic. Percy and Aquaman have to team up, with Percy bringing his demigod skills and knowledge of Greek mythology, and Aquaman his Atlantean powers and understanding of the ocean depths. They would face challenges like underwater mazes, and magical barriers as they try to stop the monster.
In the fanfiction, it could start with Bella Swan having strange dreams about an underwater world. One day, she accidentally discovers a portal that leads her to Arthur Curry's realm. Arthur is initially suspicious of this strange human from another world. However, as they interact more, they find that they have a special bond. They might have to face challenges together, like an evil force that wants to destroy both their worlds. Their relationship as mates could be the key to uniting their two very different realms and saving them from destruction.
A plot might involve Harry Potter being sent to the underworld on a quest. Hades mistakes him for a threat at first. But as Harry shows his courage and resourcefulness, Hades starts to respect him. They could end up working together to stop a dark force that is threatening both the wizarding world and the underworld. Harry could teach Hades some magic spells, and Hades could show Harry the hidden powers of the underworld.
One possible plot could be that Alduin somehow enters the Harry Potter universe. Maybe he is summoned by a dark wizard who wants to use his power to take over Hogwarts. Harry and his friends then have to figure out how to send Alduin back to his own realm while also dealing with the chaos the dragon has brought to the school.
One possible plot could be that Boromir somehow gets transported to the wizarding world of Harry Potter. He could be mistaken for a Muggle at first, but his warrior skills and strong sense of honor quickly earn him respect. Maybe he joins the Order of the Phoenix and uses his combat experience to fight against the Death Eaters. He might also form an unlikely friendship with Harry, learning about magic and teaching Harry about his own world's combat strategies in return.