A really interesting plot would be a competition of sorts between the two worlds. Since they are cousins, they are in a unique position to bridge the gap. But there are those in both worlds who are against the mixing. Harry and Percy have to prove that their combined heritage can bring great things. They could participate in a series of challenges that test both their magical and demigod abilities.
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.
Another plot could involve them exploring their family history together. They might find out that there was a long - hidden reason why their families were separated. Along the way, they encounter various mythical creatures from both their worlds. Percy could introduce Harry to the hippocampus in the sea, while Harry could show Percy some magical creatures in the Forbidden Forest.
One plot twist could be that they discover they are cousins much later in their respective adventures. For example, Percy might be on a quest in the Underworld and find out some long - hidden family secret that links him to Harry. Another could be that a seemingly friendly character turns out to be the one trying to keep them apart because their combined power is a threat to their evil plans.
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.
A cool plot could be that they are brought together by a prophecy. Percy's skills with water and Harry's magic would be combined to defeat an ancient evil. They might start by being suspicious of each other, but as they learn about their shared heritage, they grow closer. Also, there could be a plot where they have to deal with the politics of both their worlds. How would the wizards react to the existence of demigods and vice versa? This could lead to some really interesting character interactions and story developments.
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.
Here's a plot. Percy and his cousins are invited to a special tournament among demigods from all over the world. But it turns out to be a trap set by an evil force that wants to use their combined powers for its own dark purposes. As they fight to escape, they learn more about their individual strengths and how to work together as a family. They also meet some interesting new characters from different mythologies during their struggle, and these new allies help them in unexpected ways to defeat the evil force and save the day.
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 possible plot idea could be exploring how the other gods react to Artemis being pregnant. Since she is the virgin goddess, it would be a huge shock. Another idea could be about the challenges she faces while pregnant, like dealing with her own identity crisis as it goes against her long - held virgin status. Maybe there could be a story arc where she tries to hide the pregnancy from certain gods who might not take it well.
One plot idea could be that they discover their family connection early on. Maybe they find a hidden family tree or an old letter that reveals the truth. This could lead to them having to work together secretly to protect their newfound family bond from the wizarding world's prejudices.
A plot where the villains from both universes team up. Voldemort and the Titans or Giants could join forces. This would force Percy and Harry to put aside their differences and work together. They would need to combine their unique powers and knowledge. Percy's ability to control water and his combat skills along with Harry's magic skills and knowledge of the wizarding world's secrets would be crucial in fighting this powerful alliance.