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.
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.
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.
First, do your research on Ancient Greek mythology. Know the gods, the monsters, and the heroes well. For example, if you're writing about Percy facing the Minotaur, you need to know all the details about it from the original myths. Second, stay true to the characters of the Percy Jackson series. Percy is brave but also has a sense of humor, so keep that in his character. Third, create an engaging plot. Maybe it could be about Percy finding a lost temple in Ancient Greece that holds a powerful secret.
The gods also interact with Percy a lot. Zeus might be angry with Percy for interfering in the affairs of the gods in Ancient Greece. Or Poseidon could be guiding Percy secretly, giving him hints on how to deal with the challenges he faces, like when he's on a quest related to the sea.
One interesting adventure could be Percy exploring the lost city of Atlantis in Ancient Greece. He might face sea monsters and ancient traps while trying to uncover the secrets of the city.
Percy going to Ilvermorny would be a wild ride. First, he'd be amazed by the castle itself. The four houses would be a new concept for him. He might be sorted into a house based on his heroic nature, like Thunderbird perhaps. He'd introduce the idea of Greek gods to the students there, which would cause quite a stir. And his relationship with Annabeth would be put to the test as they are separated by different magical institutions.
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.