An interesting character could be a daughter of Hecate who has the ability to see into different dimensions. She often gets lost in her visions and has trouble distinguishing between the real world and the other dimensions. But when she focuses, she can provide crucial information about the whereabouts of enemies or hidden treasures.
There could be a satyr who is an amazing inventor. He creates all kinds of gadgets to help the demigods in their quests. For example, he might make a device that can detect monsters from a long distance or a shield that can adapt to different types of attacks. He could be a bit of a comic relief but also a valuable asset to the team.
A character like a time - traveling demigod from the future could be really interesting. This character could have knowledge of events that are yet to happen in Percy's world and could either help or hinder him depending on their motives.
You could have a character like Marie, a young demigod with the power to control the wind. She grew up in New Orleans and knows all the secret alleyways and hidden places in the city. Another could be Jacques, an old Cajun fisherman who is secretly a protector of a magical spring near the bayou and has some knowledge of the ancient Greek magic that Percy is familiar with. And then there's Lila, a voodoo priestess - in - training who teams up with Percy to fight against a common enemy.
A demigod with the power to control time in a very limited way. For example, they can slow down time for a few seconds during a battle, which could be a very interesting addition to the story. They could be an ally or an antagonist depending on their motives.
An ancient demigod who was frozen in time and now awakens in the modern Percy Jackson world. This character has archaic ways of thinking and fighting but also has knowledge of long - forgotten prophecies and secrets that could either help or hinder Percy. They might have a different view on the gods and their roles compared to the modern demigods. For instance, they could believe in more direct worship and obedience, which would clash with Percy's more laid - back attitude towards the gods.
Nico di Angelo is often overlooked compared to Percy. He has such a rich backstory with his connection to the Underworld and his struggle with his identity. Fanfiction could explore more of his inner thoughts and his relationships, especially his friendship with Percy on a deeper level.
Annabeth could definitely be one of his main allies. Her intelligence and strategic planning would be invaluable in a fight against Olympus. Also, Grover might be there, using his skills as a satyr to gather information and support from other nature - related beings. Some of the less - well - known demigods from Camp Half - Blood could also join in, seeing Percy as a chance for a new order.
His friends from Camp Half - Blood would be his allies for sure. Annabeth, with her strategic mind, would be invaluable. Grover, the satyr, could help Percy communicate with nature spirits which could be useful. But also, some of the minor gods who feel left out by the major Olympians might side with Percy. For example, Hecate could use her magic to assist Percy, seeing him as a chance for a new order in the Olympian world. There's also Tyson, Percy's cyclops half - brother, who would be a strong and loyal ally.
You could add a new demigod character. Maybe a child of Hecate who can use magic in interesting ways around the school. For example, she could make the lockers disappear or change the school cafeteria into a magical forest for a short time. Another character could be a satyr who is pretending to be a normal student but is really there to protect the demigod students. He could be the one who always seems to be eating strange things from his backpack, like enchanted herbs.
Percy himself is always a popular choice. You can explore his growth, his relationships, and his new adventures. Another is Annabeth. You could write about her architectural projects in relation to the Olympian world or her further adventures in wisdom - seeking.
A shape - shifting creature that can take on the form of any animal. It starts off as an enemy, trying to steal something important from Percy and the Wanderer, but later realizes they are on the same side and becomes an ally. This character could bring a lot of action and mystery to the fanfiction.