Well, of course, the oc who is the son of Gaea is a main character. There might also be other demigods or mythical beings like centaurs or satyrs that interact with him. Maybe there's a wise old druid who serves as a mentor to the oc, guiding him in understanding his powers.
In this fanfiction, Harry Potter is the central figure as he is the son of Gaea. His friends, Hermione Granger and Ronald Weasley, will surely play significant roles. They would be there to support Harry and help him navigate through the new challenges that come with his new identity. Additionally, there could be characters from Gaea's lore. For example, there might be a centaur who has knowledge about Gaea and can guide Harry. Or perhaps a demigod from Greek mythology who has some connection to Harry's newfound heritage. These new characters would add more depth and complexity to the story.
There could be a story where the oc son of gaea has to team up with other demigods to save the world from a great threat. In this fanfiction, he uses his unique connection to the earth to find hidden ancient powers that can help in the fight.
Obviously, the oc (original character) who is the son of Batman is a main character. He's likely to be the central focus of the story.
Obviously Naruto himself. There would also likely be his friends like Sasuke, Sakura, and Shikamaru. His teachers like Kakashi and Iruka could also be in it. And since it's related to Gaea, there might be some characters representing the power or influence of Gaea, maybe some nature spirits or guardians.
Gaea herself would obviously be a main antagonist. She has the power to manipulate the earth and all its forces against Percy. Her children who are fully committed to her cause could also be major antagonists. They might have powers related to the earth and be very difficult for Percy to defeat.
Obviously, Percy will be the main character. He is the one doing the destroying after all.
Obviously, Percy and Gaea would be the main characters. But there could also be other characters like Annabeth. She might be heartbroken at first when she hears about Percy's marriage to Gaea. And then there could be some of the other demigods like Jason or Piper who would be involved in trying to understand what's going on and maybe even stop it if they think it's a bad thing.
Obviously, the OC son of Zeus is the central character. He's the one around whom the story revolves. But other common characters include Zeus himself. His presence, even if not always physical, looms large as the father of the OC.
The main antagonists could be the Olympian gods. Since Percy is now the eldest son of Gaea, they might see him as a threat. They could send their own demigod champions to stop Percy if they think he is going to follow in Gaea's footsteps.
The other gods might be antagonists. Since Percy is the son of Gaea and Pontus, the Olympian gods could see him as a threat. They might be worried that he'll side with his primordial parents and disrupt the balance they've been trying to maintain. So, they could send their demigod children or even some minor gods to oppose Percy.