If Percy Jackson goes to Valhalla in fanfiction, it could be a really interesting crossover. He'd be out of his normal Greek mythology setting. He might find the Norse afterlife very different from what he's used to in the Underworld. For example, the feasting and fighting in Valhalla would be a new experience for him. And he could share his own adventures from the Greek world, which would surely amaze the Norse inhabitants.
Well, he might meet some really tough Norse warriors. Maybe he'd get into some epic battles or challenges. He could also make new friends or enemies among the Norse gods and heroes there.
If Percy Jackson goes to Valhalla in fanfiction, he could meet a whole bunch of Norse heroes. There's Sigurd, the dragon - slayer. And then there are the Valkyries who choose who gets to go to Valhalla. He might also run into Loki, who is always causing some sort of trouble. Percy would be in for quite an adventure as he tries to figure out who he can trust among these new and often unpredictable characters.
Percy going to Ilvermorny would be a wild ride. First, he'd be amazed by the castle itself. The four houses would be a new concept for him. He might be sorted into a house based on his heroic nature, like Thunderbird perhaps. He'd introduce the idea of Greek gods to the students there, which would cause quite a stir. And his relationship with Annabeth would be put to the test as they are separated by different magical institutions.
Well, if Percy goes to the past in fanfiction, he could encounter younger versions of the gods. Maybe he would befriend a young Zeus or Poseidon before they became so powerful and full of pride. He could also learn new and forgotten magic or fighting techniques that were lost over time.
If Percy Jackson goes to Hogwarts in fanfiction, he would face a whole new set of challenges. The magical rules there are different from what he's used to. He'd likely be confused by spells at first. However, his combat skills would be really useful in Defense Against the Dark Arts classes. He could show the Hogwarts students some new fighting moves. And his demigod status would make him a bit of an outcast, but also someone very interesting. I think the teachers would be both intrigued and worried about him. He might also introduce some Greek mythology elements to Hogwarts, like the stories of the gods, which could be fascinating for the students there.
Percy might run into Loki. Loki is known for his trickery. He could either befriend Percy for his own devious plans or try to deceive him. Percy, being used to dealing with tricky situations in his own world, would have to be on his guard against Loki's schemes.
If Percy Jackson goes to protect Hogwarts in fanfiction, it'd be an amazing crossover. Percy is used to facing all kinds of monsters, and at Hogwarts, he'd have to adapt to magic. He might form an alliance with some of the Hogwarts students. His speed and combat skills could help in protecting the school from any invaders, whether they be Death Eaters or other dark creatures.
Well, Percy might be really confused at first. Mystic Falls has all those vampires and supernatural stuff, while he's used to Greek gods and monsters. He could probably use his water powers to his advantage, like putting out any fires started by vampires or something. Maybe he'd make some new friends among the Mystic Falls gang, or he could end up in a fight with some of the bad vampires who might see him as a threat to their power in the town.
Well, one possibility could be that Percy discovers a new aspect of the mythological world. Maybe in this fanfic, his death is a sacrifice to save his friends. Once in Valhalla, he could meet new heroes from different mythologies and form alliances or rivalries. He might also try to find a way back to life or to his friends in the world he left behind.
In a fanfic where Percy goes to Hogwarts alone, he could form some interesting friendships. He might befriend Neville, who is also a bit of an underdog. Percy could teach Neville some of his own courage -building techniques. And he would surely be a star in the Quidditch field with his athletic abilities, even if he has to learn the rules first.
In fanfiction, if Percy Jackson goes to highschool, he might face challenges like hiding his demigod powers from his classmates. He could also encounter new mythical creatures that are drawn to the school environment.