The plot might involve Percy gathering ancient artifacts or allies. He could go on a quest to find a weapon that can harm Gaea on a fundamental level. Along the way, he overcomes many challenges and personal demons. When he finally faces Gaea, he combines his strength, the power of his friends, and the magic of the artifacts to completely destroy her, bringing peace to the world of the gods and demigods.
Obviously, Percy will be the main character. He is the one doing the destroying after all.
One possible plot could be Percy having to overcome some sort of magical or divine interference. Maybe he has to prove his worth to Gaea in a series of trials. Another aspect could be how the other demigods react to this union. Some might be in shock, while others might try to stop it for the greater good.
In a 'Percy Jackson Husband of Gaea' fanfiction plot, perhaps there's a prophecy that foretells of Percy being united with Gaea. Percy initially resists, but as events unfold, he realizes that there's more to Gaea than just the evil entity he thought she was. They could start to work together to bring about a new order in the world of the gods and demigods. Along the way, they face opposition from other gods who see their union as a threat. Percy has to balance his loyalty to his friends and his new - found relationship with Gaea, all while trying to understand his role in this strange new world order.
In this fanfiction, there could be a prophecy about a lemon that will either save or doom the world in the face of Gaea's threat. Percy Jackson is tasked with finding this lemon. Along the way, he meets various characters who either help or hinder his quest. When he finally finds the lemon, he has to make a difficult choice. If he gives the lemon to Gaea, she might spare some of his friends but would gain enough power to cause great destruction. If he destroys the lemon, he risks angering Gaea and starting a full - scale war. So, he has to find a third option that no one has thought of before.
One possible plot could be Percy discovering his true parentage as Gaea's eldest son and struggling with the implications. He might have to face the wrath of the other demigods who see Gaea as an enemy. For example, he could try to convince his friends like Annabeth that he is still on their side despite his newfound origin.
The plot could involve Percy's journey to discover the true meaning of being the son of Gaea and Pontus. He could be on a quest to find out more about his parents' realms and how they interact with the world of the demigods. Along the way, he may encounter mythical creatures that are related to Gaea and Pontus, and he has to either fight them or make peace with them. There could also be a sub - plot about Percy's relationships with his friends at Camp Half - Blood, as they struggle to accept this new side of him.
In this fanfiction, perhaps Gaea discovers a way to use the chakra in Naruto's world to strengthen her own power. She sends her minions to capture ninja who are strong in chakra. Percy Jackson, who has a connection to the spirit world, senses this disturbance and travels to Naruto's world. Naruto and Percy meet and realize they have to work together. They gather allies from both worlds, like Naruto's friends from Konoha and Percy's demigod friends, and fight against Gaea and her forces.
Well, it could be a really wild ride. Percy joining Gaea would be such a shock to his friends. They would probably think he's been brainwashed. And Percy himself might be in for a rude awakening when he sees Gaea's true intentions. She could be using him to get to other demigods, or to start a war between the gods and the demigods. He'd have to figure out a way to break free from her influence before it's too late.
One possible plot could be Percy's internal struggle. Since Gaea is often seen as a villain in the Percy Jackson series, Percy would have to come to terms with his dark heritage. He might be shunned by his friends at first. But then, as he discovers that he has the power to control earth and sky elements from his parents, he could use it for good. For example, he could prevent natural disasters that Gaea might have caused in her malevolent state. And he would have to prove to everyone that he is not like his mother, but a hero in his own right.
One potential twist could be that Percy is actually undercover for the good guys all along while pretending to join Gaea.