I got this idea from: PercyFanHoO AKA AggroPJO AKA Nyad (it wouldn't let me tag them for some reason)

They write pretty well btw, and they have a lot of nice fanfics, so you should all check out their stories. They also have the first chapter of this story idea written, so you can always use that as a starter and build off of it.

Link to their story: story/281362773-the-demigod-magician

Link to their profile: user/PercyFanHoO

Anyway, this is a crossover between Percy Jackson and Kane Chronicles.

Title: A Demigod Magician

Plot: Percy is a demigod, but he ends up going to Camp Half-Blood at the age of 8. In other words, he does everything that happens in the actual books, but just 4 years earlier, so by the age of 12, the Titan War has already been won. When Percy got home after the war, he was planning to relax and have some fun for once, but then sees a bunch of monsters at his house, many of which Percy had never fought before. He's confused as to what these monsters are and why they're attacking him. After saving his mom and Gabe, they tell him to find the Kanes, his only living relatives, who stay in the UK, promising that they will explain everything to him.

Beginning: Percy has just gotten home after the titan war. To his shock, he sees a large assortment of unfamiliar monsters outside his door. He defeats the monsters and saves Sally and Gabe from certain death. Sally, who recognizes some of these monsters from Egyptian Mythology, thinks back to her only living relatives in the UK, who she knows are magicians. She then tells Percy to go to the UK and stay with his cousins, where everything will finally be explained.

Future: You can take this story in just about any direction you want. One idea is that neither Sadie nor Carter know about magic yet. Percy arrives in the UK just a week before Julius Kane comes to take Sadie and Carter out for Sadie's birthday. Seeing Percy there, he decided to bring him along as well, and the events from The Red Pyramid are set into motion. Everything will be similar to the actual story, just that this time, Percy will be there with Carter and Sadie to help them in their mission. The rest of the arcs (The Throne of Fire and The Serpents Shadow) can also be kept similar to the actual stories with the inclusion of Percy.