In a 'Percy Jackson Banished Hero' fanfiction, Percy could be banished due to a prophecy that was misinterpreted. He ends up in a parallel dimension where the rules of the demigod world are different. There, he discovers a group of outcast demigods like himself and together they form a resistance against a powerful dark force that is trying to invade both their dimension and the original demigod world.
One idea could be that Percy is banished because of a false accusation of using his powers for evil. He then has to journey through unknown territories, facing new monsters and making unexpected allies to prove his innocence. Maybe he meets an ancient and forgotten god who offers him a deal to regain his status.
One plot idea could be that Percy is betrayed by a close friend who is jealous of his powers. This friend spreads false rumors about Percy being a threat to Camp Half - Blood. As a result, he is banished. Percy then has to prove his innocence while on his own, facing various monsters and challenges that test his strength and loyalty.
One idea could be Percy having to face a new and powerful underwater monster that is immune to his usual water - based powers. He'd have to rely on his wits and the help of his friends in unexpected ways. Another could be a time - travel story where Percy goes back to the era of the first demigods and has to learn from them to solve a modern - day problem. Maybe he teams up with an ancient hero and they combine their powers.
One idea could be Percy facing a new and powerful enemy that is immune to water, which forces him to develop new skills. Another could be Percy becoming a king in a new underwater realm and having to deal with political intrigue among the sea creatures. Maybe he has to unite different mythological groups under his leadership to face a common threat like an ancient primordial being awakening.
Perhaps Percy is banished with some of his friends, and they have to build a new society on the island. There could be internal conflicts as they struggle to adapt to their new situation and different leadership styles emerge. Percy has to navigate these relationships while also finding a way to get back home and clear his name if he was wrongly banished.
It could be a rogue demigod who has a vendetta against Percy. This demigod might have spread the false rumors that led to Percy's banishment in the first place, and now he wants to make sure Percy never returns. He uses his own powers and manipulates other demigods and monsters to achieve his goal.
One plot idea could be Percy having to team up with Hera to rescue a group of demigods who have been captured by an ancient monster. Hera, despite her usual aloofness, realizes she needs Percy's unique skills.
Well, perhaps the god in question has been misusing their powers and causing harm to mortals and demigods alike. Percy, being the hero he is, decides to take matters into his own hands and banish the god. After the banishment, Percy then has to find a way to fill the void left by the god. He might have to take on some of the god's former responsibilities, which is no easy feat as he is still just a demigod.
One possible plot could be that in a world where the gods of Percy Jackson and the Avengers co - exist, Percy is somehow tricked or forced to banish the Avengers. Maybe there's a power struggle among the gods and they see the Avengers as a threat to their power, so they use Percy, who has a strong connection to the divine world, to get rid of them. Percy might be conflicted as he may admire the Avengers' heroism but has to follow the gods' orders.
A plot could be that Sally Jackson plants a lemon tree in her garden that turns out to be a gift from a minor goddess. The lemons from this tree have the power to give those who eat them the ability to see through illusions for a short time. Percy uses these lemons to his advantage when he is on a mission to retrieve a powerful artifact that is guarded by a monster that uses illusions to protect it.
Perhaps a fanfiction where Percy and Thalia are transported to an alternate dimension. In this new world, they have to figure out how to get back while also dealing with different versions of their friends and enemies. Thalia might have to face an alternate version of herself who has turned evil, and Percy could be the one to help her see the light again. It would be full of action, drama, and self - discovery.