There's a good chance he'll meet the goddess Athena. Since Percy has a connection to the world of the gods, and Athena is known for her wisdom and strategic thinking, she could offer Percy some valuable advice. Maybe she'd help him navigate the complex social and political situations in ancient Greece or teach him some new ways to use his demigod powers.
He could have adventures like battling mythical creatures. For example, fighting the Minotaur in the labyrinth. Maybe he'd also encounter the gods and goddesses and get involved in their power struggles.
In many fanfictions, Percy is likely to meet ancient Greek heroes such as Heracles. They could engage in some friendly competitions or Heracles could offer his strength to help Percy in a difficult situation. Another character he might come across is Pandora. She could be either a help or a hindrance depending on the plot of the fanfiction as she is associated with the box that contained all the evils of the world.
Well, often in these fanfictions, Percy gets to interact with the ancient Greek heroes in a more in - depth way. He could team up with Achilles and learn some new combat skills from him. And he might be involved in some sort of mystery that is related to the lost artifacts of ancient Greece. Maybe he has to find a certain magical item that was once used by Zeus himself to save the world from a new threat.
His birth could introduce new prophecies. For example, the oracles might start predicting things related to Percy's fate that could change the course of events in Greek mythology.
One great 'Percy Jackson Ancient Greece Fanfiction' is 'The Lost Hero's Quest in Ancient Greece'. It has an exciting plot where the characters are plunged into a forgotten part of Ancient Greek mythology. The author does a wonderful job of weaving in the familiar elements from the Percy Jackson series with new and unique twists from Ancient Greek lore.
One common theme is time - travel. Since Percy is from a modern - day setting in the original series, sending him back to ancient Greece allows for all kinds of interesting scenarios. Another theme is the interaction with the Greek heroes and gods. Writers often explore how Percy would interact with the likes of Achilles or Apollo.
One common theme is the exploration of ancient Greek mythology. Since Percy is in Ancient Greece, there are a lot of opportunities to delve into the stories of the gods, heroes, and monsters.