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.
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.
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.
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.
One idea could be that Percy has unique powers given to him by Chaos. For example, he might be able to control the very fabric of the universe in small ways. Maybe he can manipulate time on a very limited scale, like slowing it down during a fight to gain an advantage.
One idea could be that Percy is raised by Poseidon. He grows up with a deep understanding of the sea and its powers from an early age. This might lead to him having a more solitary childhood as he has to hide his connection to the god. Another plot could involve Percy being raised by Athena. He would then be extremely intelligent and strategic, perhaps getting into trouble at school for being too smart. A third idea is if he's raised by Apollo. He could have a natural talent for music and healing, and his adventures might revolve around using these gifts in a world that is both dangerous and full of mythical creatures.
Perhaps Percy raised in Atlantis could be involved in a mystery related to the ancient history of Atlantis. There could be a hidden power or artifact that he has to find before the wrong people do. As he searches, he uncovers secrets about his own family that are tied to Atlantis. Along the way, he has to face challenges like underwater monsters that are specific to the Atlantean depths and overcome them using his wits and powers.