A possible plot is that Voldemort discovers the existence of the demigods and tries to use their powers for his own evil purposes. He sends his Death Eaters to capture some demigods. Percy and his friends manage to escape and seek refuge at Hogwarts. At Hogwarts, they learn about magic in a whole new way while also teaching the wizards and witches about their own powers. The two groups then have to combine their skills, like the demigods' combat abilities and the wizards' spell - casting, to fight against Voldemort and his new - found allies from the world of Greek mythology.
One great example could be a story where Percy and his friends from Camp Half - Blood end up at Hogwarts. Maybe they are there to help fight a new dark force that threatens both the wizarding world and the demigod world. In this crossover, Percy could use his water - controlling abilities in the Hogwarts lake, and Harry could show Percy some cool magic spells.
Friendship and loyalty are also big themes. Since it's a crossover, the characters from both series have to learn to trust and work together. The harem aspect adds another layer to this, as the relationships between the characters are more complex. For example, they might have to protect each other not just as friends but also as part of the harem - like group.
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.
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.
There's a fanfic called 'The Quest Beyond Worlds'. It takes Percy and Harry on a cross - universe adventure. It delves deep into the mythology of both series, making it a very engaging read. It also has some great character development for both Percy and Harry as they learn from each other's worlds.
One possible fanfic could be where Harry Potter, in a time of great need in the wizarding world, unknowingly summons Percy Jackson. Percy arrives, confused but ready for an adventure. He might bring his unique demigod powers like controlling water and his sword fighting skills to help Harry against dark wizards. The two could have an initial clash of cultures, with Percy being used to the Greek mythology world and Harry to the wizarding world.
Nico di Angelo would be an interesting choice. His dark and brooding nature along with his powers over the dead would be a contrast to the more light - hearted aspects of the Harry Potter world in some ways. He could introduce the wizards to the concept of the Underworld and the spirits. And his ability to shadow - travel could be used in some really creative ways, like getting the group in and out of dangerous situations quickly, whether it's in Hogwarts or in the magical areas related to Greek mythology.
Hermione Granger and Annabeth Chase would make a great pair. Hermione's vast knowledge of magic and her intelligence could be combined with Annabeth's strategic thinking and knowledge of Greek mythology. They could work together to solve the complex problems that would arise in a crossover situation, like deciphering ancient spells or understanding the motives of the gods.
The magic in Harry Potter and the demigod powers in Percy Jackson could interact in really cool ways. For example, a wizard's spell of protection could be enhanced by a demigod's aura of strength. If a demigod was in a fight at Hogwarts, a wizard could cast a spell to make the demigod's weapon more powerful, like making Percy's sword glow with an extra magical edge.