It could be an old enemy from Percy's past life who has also found a way to be reincarnated. This enemy might hold a grudge against Percy for something that happened in their previous encounter and is now seeking revenge in this new life.
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.
He could also become withdrawn and depressed. Percy and Annabeth have a very strong bond, and her death would leave a huge void in his life. He might isolate himself from his friends and family, lost in his grief and memories of her.
Rebuilding is also a theme. After Percy's death, the world around the characters might be in chaos. So, in many fanfictions, they have to work towards rebuilding what was lost, whether it's a physical place or the sense of hope that Percy once brought.
Definitely. One type of Percy is reincarnated fanfiction could involve him coming back as a different species. Maybe he's reincarnated as a faerie or a magical creature. In these stories, he often has to learn about his new form and how to survive in a world that may be very different from what he knew before.
One common theme is identity. Percy has to figure out who he is in his new life. Is he still the same hero? Another theme is redemption. Maybe he made some mistakes in his past life and his reincarnation gives him a chance to make things right.
Percy might become more independent. Without his mom's presence, he has to rely more on himself. He could start to take on more leadership roles within the demigod community. He also may develop a darker side to his personality, as the pain of his mom's death lingers. However, through his experiences and the support of his friends, he gradually learns to balance this new, harsher side with his original kind - hearted nature.
In this fanfiction, Percy might sacrifice himself in a grand battle. He could be facing a powerful enemy that was about to strike Zoe. Percy, being the heroic type, jumps in front of Zoe at the last moment. His last thoughts could be of his friends and all the adventures he had. Zoe, in turn, is left with a deep sense of guilt and sorrow, vowing to carry on Percy's legacy. She might become even more determined to fight for the cause they both believed in, all while mourning the loss of her dear friend.
In this kind of fanfiction, it's often a very tragic and heroic concept. Percy sacrificing himself to save the seven would be a huge shock to the other characters. It might lead to a lot of grief and also a new sense of purpose for the remaining seven. They would have to carry on with their mission while also dealing with the loss of Percy, which could add a lot of depth to their character development.
In this type of fanfiction, it's a really interesting concept. One possible scenario could be that Percy's death is a heroic sacrifice. Maybe he gives his life to save the world from an even greater threat than before. And when he becomes a god, he might use his new powers to bring about a new era of peace among the gods and demigods. His transformation could also mean changes in his relationships. For example, his friends might now have to view him in a different light, as a divine being rather than just a fellow demigod.