In a 'Percy Jackson Son of Kronos and Gaea Fanfiction', a great plot could be Percy being hunted by both the Olympians and the Titans because of his unique parentage. He then has to go on a journey to find a place where he can belong. Along the way, he meets other demigods who also have mixed or unusual lineages. They form a sort of outcast group and together they try to prove that their existence doesn't have to be a threat but can be a new source of balance in the world of gods and mortals. This journey would be full of self - discovery for Percy as he learns more about his parents and what it means to be their son.
One idea could be Percy having to choose between the powers of Kronos and Gaea. Another could be Percy teaming up with some unexpected allies from the realms of Kronos and Gaea to fight a new common enemy. Maybe Percy discovers a hidden prophecy that involves his lineage as the son of Kronos and Gaea and has to fulfill it to save the world.
One idea could be Percy having to face challenges in a world where Gaea has more direct control over the elements. For example, the earth itself could be constantly shifting and changing, creating new terrains and obstacles for him to overcome. Another could be Percy forming an unlikely alliance with some of Gaea's other children who are also having second thoughts about their mother's destructive plans.
Another plot could involve Percy being sent on a quest by the gods to find a way to sever his connection to Kronos completely. Along the way, he meets new allies and enemies, and has to face challenges that test his loyalty to both his new identity and his old friends.
One idea could be Percy struggling with the dark influence of Kronos while still trying to maintain his loyalty to his friends at Camp Half - Blood. Another could be Percy having to hide his true identity as Kronos' adopted son from his closest allies. Maybe he discovers some long - lost powers or knowledge that Kronos had hidden away for him, which he must use to either save or destroy the world of the gods.
A great plot could also involve the OC forming an unlikely alliance. He could team up with some of Percy Jackson's friends, like Annabeth. They initially don't trust him, but as they face challenges together, they realize that he's not like his father. This alliance could lead to them facing off against an ancient evil that only the combined knowledge and powers of the OC and the other demigods can defeat.
Well, perhaps a plot where Percy has to enter Kronos' old lair to find a way to break a curse that is affecting his friends. He could face many challenges and traps there. Also, a plot where Percy discovers that Kronos had a secret plan that he now has to carry out, but it conflicts with his loyalty to the Olympians.
Well, a possible plot could be Percy being sent on a quest by Gaea. But instead of following her orders blindly, he uses the quest to gather information about her weaknesses. He could form an unlikely alliance with some minor gods who also oppose Gaea. As for his relationship with his old friends, they would be in shock and some might even try to 'rescue' him from Gaea's influence, leading to some tense and emotional encounters.
Perhaps the Daughter of Gaea is sent on a mission by Gaea to infiltrate Camp Half - Blood. But instead of causing harm, she falls in love with the sense of community there. She starts to secretly help the campers prepare for Gaea's attacks. She could use her connection to the earth, which is different from the demigods' but still useful, like sensing when Gaea is about to send her minions.
One plot idea could be Gaea's redemption. In the original series, she was a major villain, but in a fanfic, she could be given a chance at redemption. Maybe Percy and his friends discover that Gaea was being controlled by a more powerful and malevolent force all along, and they have to work with her to defeat this greater evil.
One idea could be Percy having to face moral dilemmas as he discovers more about his connection to Kronos. For example, he might be tempted by the power Kronos once held. Another could be Percy having to deal with the distrust of his friends who fear he'll turn into an heir of Kronos in a bad way. He could also go on a quest to find a way to sever his connection to Kronos if it's a negative one.
One idea could be Percy being forced to do Kronos' bidding while secretly trying to find a way to break free. He might be sent on dangerous quests that are actually part of Kronos' plan to gain more power. Another could be Percy having to interact with other characters who are also under Kronos' control and trying to figure out who can be trusted. Maybe he discovers a hidden power within himself that could be the key to his liberation.