One plot idea could be that Percy has to deal with the internal conflict of having two very different divine parents. Hera's strict and often - conniving nature clashes with Poseidon's more laid - back and powerful - but - less - controlling side. Another could be that the other demigods at Camp Half - Blood are initially distrustful of him because of Hera's reputation. So Percy has to prove himself not only as a powerful demigod but also as someone who can be trusted.
A cool plot idea is that Percy discovers his true parentage later in the series, after already believing he was just Poseidon's son. This revelation throws his world into chaos. He then has to go on a quest to understand why Hera was involved in his creation. Maybe it was part of a grand plan to create a demigod who could bridge the gap between the constantly - feuding gods, especially between Poseidon and Hera's husband Zeus. Along the way, he has to face monsters that are specifically targeting him because of his new - found and very unique parentage.
A plot idea might be that Percy is magically transported to a time when Poseidon and Hera had a major disagreement in the past. He has to use his wits and powers as Poseidon's son to prevent this rift from growing and causing chaos in the present. Also, he could be given a task by Hera to rescue one of her favored heroes who has been trapped by a sea monster under Poseidon's domain. This would put Percy in a tricky situation where he has to balance his loyalty to his father and the task given by Hera. He might also encounter a group of demigods who are descendants of both Poseidon and Hera in some way, and together they have to face a common enemy.
Well, Percy could be sent on a quest by Hera to reunite broken families in the mortal world. This would be in line with Hera's role as the goddess of family. As he does this, he could encounter various monsters and challenges. Along the way, he might discover that some of these broken families are the result of the interference of other gods or mythical beings. Percy would then have to use his wits and powers (as the son of Hera) to not only fix the families but also deal with the root causes of their problems. This could involve battles, negotiations, and a lot of self - discovery for Percy.
One idea could be Percy discovering his connection to Hera later in his adventures and having to deal with the reactions of his friends. Another could be him having unique powers inherited from Hera that set him apart from other demigods.
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.
One idea could be Percy having to face a new and powerful sea monster that is awakened by an ancient curse. He'd have to use his powers in unique ways, maybe even discovering new abilities as the son of Poseidon. Another could be Percy traveling to a long - lost underwater civilization that has a connection to his heritage as an ancient son of Poseidon.
A great plot could be Percy getting into trouble in the mortal world and Poseidon having to come to his rescue without revealing his true identity to the mortals. This would create a lot of tension and interesting scenarios where Poseidon has to use his powers subtly. Also, they could be on a mission to save a group of sea creatures that are being hunted by an unknown and powerful force. Poseidon could be teaching Percy about the importance of all sea life along the way.
A cool plot could be Percy being sent on a quest that involves mending the rift between Zeus and Poseidon. Along the way, he meets old foes and new allies. He has to use his wits and the powers he got from his fathers to convince other gods and demigods to support his cause. For example, he might have to show the children of Zeus and Poseidon that they can work together instead of being rivals.
One plot idea could be Percy having to team up with Hera to rescue a group of demigods who have been captured by an ancient monster. Hera, despite her usual aloofness, realizes she needs Percy's unique skills.