What could be an interesting plot for a Percy Jackson and Eragon crossover fanfiction?

One idea could be that Percy and his friends are on a quest and accidentally stumble into Alagaesia, the world of Eragon. There, they meet Eragon and Saphira. The demigods' powers might be seen as strange magic by the people of Alagaesia. Percy could use his water - controlling abilities to help Eragon in a battle against some new threat that is both a danger to the demigods' world and Alagaesia, like a powerful water - based demon. They would have to learn to work together, with Percy teaching Eragon about the modern world's concepts and Eragon showing Percy the ways of magic in his world.

The plot could involve a villain who has found a way to cross between the two worlds. This villain starts causing chaos in both the world of Percy Jackson, like turning demigods against each other, and in Eragon's world, by disrupting the dragon - rider bond. Percy and Eragon, being the main heroes, have to team up. They start by trying to understand each other's powers and the rules of their respective worlds. Along the way, they make new friends and allies from both worlds and face many challenges together until they finally defeat the villain and restore peace in both their worlds.

One possible plot could be that the Volturi from Twilight discover the existence of demigods from the Percy Jackson world. They see the demigods as a threat to their vampire supremacy. Percy and his friends have to team up with some of the more friendly vampires, like the Cullens, to fend off the Volturi. This would bring together the magic and powers of both universes in an epic battle.

Well, perhaps there's a villain in the Percy Jackson universe who discovers that the iCarly web show has a huge following and decides to use it as a way to spread chaos. The demigods have to team up with the iCarly crew to stop this. The iCarly gang has to learn about the world of Greek mythology really fast and help the demigods navigate the modern world of technology and media to defeat the villain.

The plot could involve a powerful magical artifact that has military applications. The NCIS comes across this artifact during an investigation but doesn't understand its true nature. Percy Jackson and his friends, who are on a quest to retrieve the artifact for the demigod world, cross paths with the NCIS. There is a lot of miscommunication at first as the two groups have different goals and ways of operating. But as they realize that they are both facing a common threat from a group of rogue demigods and power - hungry military personnel, they join forces. Percy uses his knowledge of the demigod world and his powers to help the NCIS agents navigate the magical aspects while the agents use their resources and combat training to take on the human threats.

One possible plot could be that the Greek gods, noticing the powerful threats the Avengers face, send Percy Jackson and his friends to help. Percy could use his water powers to assist in putting out fires during a battle like the one in New York. Meanwhile, Thor could be intrigued by Percy's connection to Poseidon and they could exchange stories about their godly fathers.

A great plot could involve a prophecy in both the Naruto and Percy Jackson worlds. The prophecy states that only by combining the powers of the ninja and the demigod can a great evil be defeated. Naruto and Percy are chosen to fulfill this prophecy. Along the way, they face challenges like trying to understand each other's cultures. Naruto has to get used to the Greek pantheon, and Percy has to learn about chakra. They also have to deal with their own insecurities. For Naruto, it could be his fear of not being strong enough without the Nine - Tails' power, and for Percy, it could be his fear of losing his friends in the battle.

One idea could be that the demigods from Percy Jackson end up in Riverdale due to some sort of magical mishap. Percy could be confused by the strange mortal world of Riverdale, with its own set of secrets and drama. Meanwhile, the Riverdale gang could be in awe of the demigods' powers. For example, Archie might be inspired by Percy's heroism and try to be more like him in facing the town's problems.

Another possibility is that Percy somehow gets transported to Eragon's world. He has to adapt to the new environment and figure out how his demigod powers work there. Eragon could initially be suspicious of Percy but then they realize they can help each other. Percy could teach Eragon about water magic, which is new in Eragon's world, and Eragon could show Percy how to ride a dragon, which would be an amazing experience for Percy.

Well, perhaps the H2O girls are being chased by some sea monsters that are normally under Percy's jurisdiction. Percy and his demigod friends come to their rescue. In the process, the H2O girls learn about the world of Greek mythology and demigods. They could then join forces to fight off other threats that come their way, like an evil sea god who wants to take over both their worlds.