Perhaps there's a character crossover in a more unique way. A demigod in the Percy Jackson world has a distant relative who was cursed in the Diablo world. This demigod, through some magical accident, gets transported to the Diablo realm. Percy, worried about his friend, follows. In the Diablo world, they have to adapt to the darker and more brutal environment. Percy has to use his skills in a different way, like his water powers to cool down the hellish fires. They meet Diablo - like characters who may not be all bad, and together they try to break the curse and find a way back home.
The demigods from Percy Jackson's world would interact with the Diablo characters in different ways depending on their personalities. Annabeth, being the strategic thinker, would try to analyze the Diablo characters' weaknesses and form plans. She might try to communicate with any intelligent Diablo creatures to find out more about their world. Grover, with his connection to nature, might be really disturbed by the corrupted and dark nature of the Diablo world. He could try to find any remnants of good or nature in that world to help in the fight against the dark forces. And when it comes to the Diablo characters, some of the more cunning ones might try to manipulate the demigods for their own ends.
One more theme could be the idea of corruption. The Diablo world is known for its corrupting influence. Percy, being a hero from a different world, may have to resist this corruption. This can create internal struggles within him as he tries to stay true to his values while dealing with the dark forces around him. And of course, the theme of adventure is always there. Exploring the unknown regions of the Diablo world, finding treasures, and fighting bosses are all things that make these fanfictions exciting.
Well, one idea for this crossover could be that Savitar somehow ends up in the world of Percy Jackson. Maybe he's chasing after some new kind of speed - the speed of a demigod? And Percy has to figure out how to deal with this strange, super - fast being who doesn't seem to follow the normal rules of the Greek myth world.
There are several fanfictions where Percy Jackson is thrown into the Diablo realm. Some explore how his powers interact with the Diablo magic system. For example, his ability to control water could have unique effects in a world filled with dark magic. He might be able to purify corrupted water sources or use water to combat some of the demonic entities. Another aspect could be his relationships with the characters in Diablo. Will he befriend the heroes there or be seen as an outsider? These fanfictions usually take a lot of creative liberties to blend the two universes in an interesting way.
Another idea is that Sophie Foster from KotLC travels to the Percy Jackson universe. She could be mistaken for a demigod at first. She would have to learn about the Greek gods and monsters. Her telepathic abilities would be really useful in the Percy Jackson world. For example, she could communicate with some of the monsters to find out their plans. And Percy and his friends would help her understand this new and dangerous world.
One idea could be that Naruto, with his powerful chakra and skills, is somehow transported to the world of Percy Jackson. He might be mistaken for a demigod because of his extraordinary abilities. Naruto could then team up with Percy to fight against a common enemy, like an ancient monster that threatens both their worlds.
Another one to check out is 'Justice League meets Camp Half - Blood'. In this fanfic, the Justice League discovers Camp Half - Blood. It's cool to see how Batman would interact with Chiron, or how Wonder Woman would view the demigod powers. There are a lot of great character moments as the two very different universes collide.
One great Percy Jackson crossover fanfiction is the one where he crosses over with the Harry Potter universe. It's exciting to see how the magic of the two worlds interact and how Percy and Harry might team up. Another good one is the crossover with the Avengers. Imagining Percy fighting alongside superheroes like Thor and Captain America is really cool.
I really like 'Percy in the Marvel Universe'. In this fanfiction, Percy gets transported to the Marvel universe. He has to figure out how to get back home while also dealing with all the superheroes and villains there. It shows his character development as he tries to adapt to this new and very different world. The story also has some interesting pair - ups, like Percy and Spider - Man becoming friends and having adventures together.