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.
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.
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.
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.
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.
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.
In this fanfiction, Percy Jackson is the central figure as he controls the Styx. But other important characters could be Grover, his satyr friend. Grover has always been there for Percy and could provide support or comical relief. Also, Nico di Angelo could play a significant role. Given his connection to the underworld, he might have some insights or even a conflict with Percy regarding the control of the Styx.
Well, Percy Jackson himself would obviously be the main character. And since it's about being a slave of the gods, gods like Zeus, Poseidon, and Athena could be important characters as well, as they might be the ones either enslaving him or having some role in his enslavement or liberation.
Obviously, Percy Jackson and Kronos are the main characters. Percy is the hero, the son of Poseidon, with his powers over water and his ability to lead. Kronos is the powerful Titan, the main antagonist, with his devious plans to take over the world.
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.