One plot idea could be that Percy and Harry discover they are long - lost brothers and have to combine their magical powers to defeat a new, powerful dark force that threatens both the wizarding world and the world of Greek gods. For example, they might have to find a way to stop a dark wizard who has made a pact with a rogue Greek god to gain ultimate power.
A plot could involve a competition between the two groups. Maybe the wizards challenge the demigods to a series of magical and physical tasks. This would lead to some really interesting interactions as they learn about each other's abilities. The demigods would be amazed by the wizard's spells and the wizards would be in awe of the demigods' powers.
One idea could be that Percy and Triton have to team up to stop an ancient sea monster that is threatening the underwater kingdom. They start off not trusting each other but as they face challenges together, they learn to work as a team.
One idea could be that Harry and Percy meet during a magical convergence. They realize they can combine their powers to fight a new, powerful dark force that threatens both the wizarding world and the world of the Greek gods. For example, Percy could use his water powers to put out a magical fire created by a dark wizard, while Harry uses his magic to protect Percy from a monster attack.
One idea could be that the twins have powers from both the wizarding world and the demigod world. They can use magic spells like in Harry Potter and also have the abilities of a demigod from Percy Jackson. For example, they can control water like Percy and at the same time cast defensive spells. Another plot could be that they are sent on a mission to stop a threat that endangers both the wizarding world and the Camp Half - Blood. They have to use their combined knowledge and skills to succeed.
One idea could be that the demigods and wizards have to team up to fight a common enemy that is threatening both the magical and the mythological worlds. For example, a dark force that can manipulate both magic and the powers of the gods. Another plot could involve Percy and his friends getting lost in the wizarding world and having to navigate Hogwarts while also dealing with their own demigod issues. Maybe they discover that some of the magic in the wizarding world has its roots in the ancient Greek magic that the demigods are familiar with.
A great plot could involve a prophecy that requires the combined powers of both demigods and wizards. For example, a dark force is rising that can only be defeated if the magic of Hogwarts and the powers of the Olympian gods work together. So, Harry Potter and Percy Jackson have to put aside their differences and form a team. Along the way, they discover that their two worlds have more in common than they thought, like the existence of different types of magic and the importance of loyalty and friendship.
One idea could be that a new character, who is a powerful wizard - demigod hybrid, enters both the wizarding world of Harry Potter and the demigod world of Percy Jackson. This character unknowingly attracts the attention of various characters from both universes, like Hermione, Ginny from Harry Potter and Annabeth, Piper from Percy Jackson, creating a harem - like situation. They all end up teaming up with this new character on different adventures, with some underlying romantic tensions.
Maybe they get transported to a strange new dimension where the rules of both their worlds are all jumbled up. They have to rely on each other to survive and find their way back home. During this time, they encounter strange creatures that are a mix of magical beasts and Greek monsters. And as they face these challenges, they grow closer as brothers and become even more powerful as individuals.
One idea could be that the wizarding world discovers the existence of demigods. Harry and his friends team up with Percy and his crew to fight a common enemy that threatens both their worlds, like an ancient, powerful dark force that feeds on magic and the power of the gods. For example, a new kind of dark wizard who has made a pact with a minor, evil god.
A really interesting plot could be that there is a prophecy in both worlds that only when Harry and Percy, as cousins, combine their powers can they defeat an ultimate evil. This evil could be something that has been lurking in the shadows of both universes, waiting for the right moment to strike. As they try to fulfill the prophecy, they have to learn about each other's powers and cultures. Harry would learn about the Greek gods and Percy would learn about magic spells. Along the way, they might face internal conflicts within their own communities who are skeptical or even against this union of the two different worlds.