Well, one possible plot could be that the gods in the Percy Jackson universe notice some strange energy disruptions caused by the Infinity Stones in the Avengers' world. Percy and his friends are sent to investigate. They meet the Avengers and at first there are misunderstandings, like the Avengers thinking Percy's powers are from some new form of alien technology. But then they realize they need to work together to stop a common enemy, perhaps a new powerful being that is drawn to the combined power of the demigods and the Infinity Stones.
The plot could involve Percy Jackson's world of Greek gods colliding with the Avengers' universe. Maybe the gods have some sort of issue that only the Avengers' powers can help with, or vice versa. For example, an ancient Greek monster has been unleashed in the modern world that the Avengers are struggling to defeat, and Percy and his friends come in with their knowledge of Greek mythology to assist. It could also be a situation where the Avengers are dealing with a threat that has its roots in Greek magic, and they need Percy's demigod powers to counter it.
One way could be to have Percy Jackson's powers of being a demigod interact with the superpowers of the Avengers. For example, his ability to control water could be used in a joint mission with Thor's lightning powers. Maybe they are facing a common enemy that can only be defeated by combining their unique skills.
Percy Jackson and Thor would be an interesting pairing. Percy has his water powers and connection to the sea, while Thor has his lightning powers. They could have some really cool battle scenes together, like when they face a water - and lightning - based enemy. Also, they both have a bit of a sense of humor and a heroic nature, so they'd probably get along well.
A Percy Jackson and Avengers crossover fic could be really exciting. Imagine Percy's water powers combined with Thor's lightning. They could create some really powerful elemental attacks. And the Avengers could be baffled by Percy's ability to talk to sea creatures. Maybe they'd team up to fight a common enemy like a new super - powerful Titan or a group of evil Asgardian - Greek hybrids.
I think Percy Jackson and Thor would make an interesting pairing. Percy has his power over water and is a skilled swordsman, while Thor has his mighty hammer and control over lightning. They both come from different worlds of power but have a lot in common. They could have some epic battles together against common enemies, like frost giants or sea monsters. And they could also exchange stories about their respective homes and families.
One plot idea could be that Percy Jackson discovers a magical artifact that somehow links his world to the Marvel Universe. Thor senses the power of this artifact and comes to investigate, leading to a meeting with Percy. Meanwhile, the Avengers also get wind of it and think it could be a threat. So, they all end up in a big showdown where they have to figure out if they're on the same side or not.
In such a crossover, there could be epic battles. Percy might use his water - controlling powers against the Avengers' enemies. Maybe Thor and Percy would have an interesting encounter, comparing their powers over elements like water and lightning.
One great 'Percy Jackson Crossover Fanfic' is 'Percy Jackson and the Avengers'. It combines the world of Percy Jackson with the Marvel universe in a really interesting way. The characters interact in a believable manner and there are some really cool fight scenes.