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 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.
In some fanfics, they might be depicted as brothers in some sort of crossover scenario. Fanfic writers often like to create unique relationships between different fictional universes' characters.
Perhaps they start off not knowing they are brothers. Harry is at Hogwarts and Percy is at Camp Half - Blood. But then strange things start to happen. They both start having visions of the other's world. Eventually, they meet and find out they share the same father. Then they go on a journey to find out more about their family history and in the process, face challenges from both the wizarding and demigod communities who are against their union.
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 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.
One common plotline is them teaming up to fight a common enemy that threatens both their worlds, like a dark wizard who also has an alliance with some Greek monsters.
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 they discover their family connection during a magical crisis. Maybe a dark force is threatening both the wizarding world and the world of the Greek gods, and their combined powers as cousins help in the fight. For example, Harry's knowledge of complex spells and Percy's control over water could be used in creative ways to defeat the enemy.
Sure. Maybe Harry is raised by Tony Stark in particular. Stark tries to understand Harry's magic and even uses some of his technology to enhance Harry's magical items. For example, he modifies Harry's wand to be more powerful. When Harry is old enough, he wants to go to Hogwarts, but the Avengers are hesitant because they don't know what kind of place it is. This creates a conflict. Or perhaps an alien race attacks both the magical world and the Muggle world, and Harry has to bring the two worlds together to fight the common enemy.
Sure. One interesting aspect of these fanfictions is how they handle the different mythologies. In the Percy Jackson series, it's mainly Greek mythology, while Harry Potter is more of a wizarding world with its own lore. When they are made brothers, fanfic writers often find creative ways to merge these mythologies. Some fanfictions might have them discover a new threat that requires both their powers and knowledge of different magical realms to defeat, which makes for a really exciting read.