Obviously, Percy Jackson and Artemis. Percy is the main character of the original series, and since he's the 'assassin' in this fanfiction, he's central. Artemis is the one he's wrongly accused of trying to assassinate, so she's also a key character.
Well, it could involve Percy being tasked with protecting Artemis in a way that goes against his normal alliances. Maybe some dark force is after Artemis and Percy has to use his skills in a new and unexpected way.
The Hunters of Artemis are very likely to show up. They are Artemis's loyal followers and would surely be involved in the search for their mistress. Annabeth could also be there. She's Percy's friend and has great wisdom, which could be useful in devising a plan to save Artemis. Grover might be another character. His ability to sense things could help in tracking Artemis or finding clues about her whereabouts.
Obviously, Percy Jackson is one of the main characters. He's a demigod with amazing powers related to water. And then there are the Artemis Hunters. Artemis herself is an important figure, though she may not be as directly involved as her Hunters. Thalia, who is part of the Hunters, is also a significant character. She has her own backstory and powers, and her relationship with Percy adds an interesting dynamic.
Obviously, Percy would be a main character, now as a daughter of Artemis. Artemis herself would also be a very important character, as Percy's new 'parent' in a sense. Annabeth could still be a main character too, as her relationship with Percy would likely change and be explored in the fanfiction.
Percy Jackson himself would obviously be a main character since it's a 'Reborn Percy Jackson Fanfiction'. His friends like Annabeth Chase are also likely to be main characters. She could play a crucial role in helping Percy adjust to his new life after being reborn. Grover would probably be there too, still being Percy's loyal friend. And the gods, especially those who have a connection to Percy like Poseidon, would also be important characters as they might have different reactions to Percy's rebirth.
There could also be some characters unique to the fanfiction. Maybe a new demigod who has some special power related to Tartarus and ends up joining Percy on his quest. Or perhaps an ancient being who was imprisoned in Tartarus long ago and has knowledge that Percy needs to complete his mission.
Percy Jackson is the central figure here. He's the one with the unique heritage as the son of Chaos. Artemis is a key character too. In addition, there might be some new characters created specifically for the fanfiction. For example, a mentor figure who helps Percy understand his chaotic powers better and how to relate to Artemis and her ways. There could also be antagonists, maybe a demigod who is jealous of Percy's special connection and tries to undermine him.
Percy Jackson himself is almost certain to be a main character. After all, the fanfiction is centered around him after the war. Annabeth Chase would also likely be a main character, as she is Percy's love interest and a powerful demigod in her own right. Grover, Percy's best friend, would probably be there too, still looking out for nature and helping Percy in his new adventures.
Percy Jackson himself would be the main character, obviously. Since he is the God of Matter in this fanfiction. His friends like Annabeth Chase would also likely be important characters. She could be there to support Percy and use her own intelligence to help him understand and control his new powers.
Obviously, Percy Jackson himself would be a main character. Since it's about him being in a god camp. Annabeth Chase is also likely to be a main character as she has always been an important part of Percy's life. Grover, Percy's best friend, would probably be there too. And there might be some new characters, like other god - like beings or powerful demigods in the camp that Percy interacts with.