Percy himself is of course a very popular character in this type of fanfiction. Since it's about his journey in the past, he's the central figure. Another popular character is Annabeth. Fans often write about her either accompanying Percy in his time - traveling adventures or being the one waiting for him back in the present while he's in the past. And then there are the gods. Zeus, Poseidon and Athena are often included as they play important roles in Percy's past - related stories.
He might use his powers over water in some creative ways. Maybe he finds a magical spring that has time - altering properties and uses it to travel back and change things.
Well, some past gods might be amused. They'd see these modern interpretations of their stories and characters in the Percy Jackson fanfiction as a strange yet interesting new form of worship or at least attention. For example, Zeus might be a bit irked at some of the liberties taken with his character, but also secretly flattered that people are still so interested in him.
Well, if Percy goes to the past in fanfiction, he could encounter younger versions of the gods. Maybe he would befriend a young Zeus or Poseidon before they became so powerful and full of pride. He could also learn new and forgotten magic or fighting techniques that were lost over time.
In a fanfiction where Percy Jackson travels to the past, he might try to prevent some of the tragedies that occurred in the past. For example, he could attempt to stop the first Titan War from starting. He might use his skills and knowledge from the present to change the course of history, but this could also have unforeseen consequences, like disrupting the timeline and creating alternate universes.
I remember reading a fanfiction titled 'Percy's Secret Quest'. It was quite long but really engaging. It started with Percy being given a secret mission by an unknown god. As he embarked on this quest, he had to face challenges that tested his loyalty and friendship. The author added some unique twists to the story, like new powers for Percy and unexpected alliances. It was really a great read for any Percy Jackson fan.
One interesting 'Percy Jackson in the past' fanfiction could be about Percy going back in time to the era of the first demigods. He might interact with ancient heroes and learn new ways of using his powers. For example, he could meet Hercules and learn some unique combat skills from him. This would add a whole new layer to his character development as he discovers different aspects of his heritage from the past.
The entire world of the story could be altered. Monsters might be stronger or weaker depending on what he changes in the past. If he stops some key event that was related to a monster's origin, it could lead to a different power balance in the world of demigods.
Percy would probably bring a sense of compassion. Unlike the traditional God of War who is often seen as only interested in bloodshed, Percy would care about the innocent caught in the crossfire. He'd use his power to protect civilians as much as fight battles.