Maybe Percy tries to break the curse. He could embark on a quest to find a powerful magical artifact or a long - forgotten spell that has the power to reverse his immortality. Along the way, he would face various challenges and meet interesting characters who either help or hinder his journey.
Another plotline could involve Percy using his immortality for good. He might become a protector of the world in a more long - term sense. He could be there to prevent major disasters in the future, and in the process, he has to deal with the fact that the world he is protecting is constantly changing while he stays unchanged.
Percy would probably develop a greater sense of patience. Since he has all the time in the world, he could learn to wait for the right moment to act. This new - found patience could help him in his adventures and in his attempts to either break the curse or come to terms with his immortality. He might also study various things over the long years, becoming more knowledgeable and wise, which would also shape his character.
One possible plotline could be that Percy has been betrayed by his closest friend. Maybe this friend revealed a big secret of Percy's, and now Percy feels isolated and heartbroken. He might start to question his relationships and his place in the world.
One possible plotline could be Percy's friends trying to break him out. They might have to overcome various obstacles like guards, traps, and security systems within the prison.
One possible plot could be Percy struggling to control new, strange powers that come with the curse. Maybe he has to constantly battle against the dark impulses the curse brings out in him.
Well, perhaps in the fanfiction, Annabeth betrays Percy's trust in a relationship way. She could start seeing someone else and use Percy's secrets against him to make herself look better in front of the new person. Or she might side with a group that Percy is against, believing their lies and false promises over Percy's warnings. This could lead to Percy feeling completely alone and having to find new allies.
Another plotline could involve Percy making new friends in the navy. These friendships could be tested during dangerous missions or when faced with internal conflicts within the naval unit.
Another plotline could be that Percy's reincarnation is part of a grand plan. There could be a powerful being or a prophecy that dictates his reincarnation. When he is reborn, he is fated to either save or destroy this new world he is in. Along the way, he meets friends from his past life who have also been reincarnated, but they don't recognize each other at first, and they have to go through a series of adventures together to remember who they really are.
One possible plotline could be that Percy sacrifices himself to save Artemis from a powerful and ancient enemy. Maybe there's a prophecy that foretells his death in order to protect her. Another could be that Percy is tricked into a situation where he has to give his life for Artemis to prevent a great disaster from befalling the world of the gods. And perhaps in his death, he becomes a symbol of heroism that changes the way the gods view demigods.
Perhaps Bianca has been poisoned, and Percy has to find a rare antidote within a time limit. He might have to journey to a far - off land, facing many challenges along the way. Or, it could be that Bianca has been lured into a trap by a false friend, and Percy has to expose the traitor and rescue her from the ensuing danger.
One possible plotline could be that Percy and Nico are betrayed by a close friend within the demigod community. Maybe they are framed for a crime they didn't commit, like stealing a powerful artifact from the gods. This could lead to them being hunted by other demigods while they try to clear their names.