One plot idea could be Percy having to go on a quest specifically guided by Poseidon's hidden messages in the sea currents. He has to decipher these messages to find a lost artifact that can save the underwater kingdom from a new, mysterious threat.
A great plot could be that Poseidon is in some sort of trouble in the Underworld, and Percy has to make a deal with Hades to get him out. But the deal involves Percy having to complete a series of near - impossible tasks, all while trying to figure out why Poseidon ended up in the Underworld in the first place.
One idea could be Percy having to face a new threat underwater that only Poseidon can help him understand. Maybe a lost civilization that Poseidon once had a connection with is now causing trouble. Another could be Percy going on a quest to find a powerful artifact that was once Poseidon's but has been stolen, and Poseidon gives him special powers or guidance along the way.
In this type of fanfiction, a possible plot is that Poseidon raises Percy away from Camp Half - Blood to protect him from the prophecy. As Percy grows up, he becomes more in tune with his water powers. He could then have adventures in the ocean, like finding lost civilizations or facing off against sea monsters that Poseidon sends his way to test him.
One idea could be her going on a quest to find a lost trident piece that was stolen by a powerful new enemy. This would involve facing various mythical creatures and using her unique powers as Poseidon's daughter.
Another plot could involve Percy being ostracized by some of the other demigods because of his father. But then, he uses his unique connection to Poseidon to prove his worth. He might be able to call on sea creatures to help in a battle or to find something lost at sea. This would show that being raised by Poseidon gives him an edge.
A possible plot could involve Percy being raised by Poseidon in a hidden underwater realm. He would be trained in the ways of the sea gods from a young age. This could include learning to communicate with all sea creatures, not just the ones in Greek mythology. He might have to face challenges like underwater mazes or taming a powerful sea monster to prove his worth as Poseidon's son. As he grows, he could start to feel a longing for the surface world and the mortals there, leading to a conflict between his loyalty to his father and his curiosity about the world above.
A great plot could be Percy getting caught in a power struggle between Athena and Poseidon's followers. Since he is the son of both, he is a symbol of unity or a threat, depending on how different groups view him. He could be forced to prove his loyalty to both sides while also trying to maintain peace among them. This could involve battles, political intrigue, and lots of character development as he tries to figure out where he truly belongs in this complex world of gods and their followers.
One idea could be Percy as a baby having small adventures in the underwater world of Poseidon. Maybe he befriends a baby sea monster. Another could be Poseidon trying to protect baby Percy from the other gods who are suspicious of this half - god baby.
Maybe Percy discovers a prophecy that involves both his father Poseidon and Lupa. He has to journey to different realms under the sea and in the Roman wolf - related places. Along the way, he meets new demigods and creatures that either help or hinder him in fulfilling the prophecy.
One interesting plot idea could be Percy having to team up with a demigod child of Leto. They could go on a quest to find a long - lost artifact that has the power to restore balance between the sea and the moon's influence. Since Percy is the son of Poseidon, his control over water and the other demigod's connection to Leto's lunar powers would create a unique dynamic.
One interesting plot idea could be Percy having to deal with the conflicting natures of his 'parents'. Since Gaia represents the earth and Poseidon the sea, he might struggle with controlling both earth - related and sea - related powers. For example, when he's near a beach, he could accidentally cause small earthquakes or make strange things happen to the sea life. Another plot could involve Percy facing a threat that only his unique dual - heritage can defeat. Maybe an ancient evil that is both of the land and the sea, and Percy has to figure out how to combine his powers in a new way to stop it.