Well, perhaps in the fanfiction, Percy discovers a prophecy that only he, as the son of Hades and Poseidon, can fulfill. This prophecy could involve saving both the Underworld and the Seas from a great evil. Along the way, he teams up with some unexpected allies like demigods from other minor godly lineages. They help him understand his powers better and together they face numerous challenges and battles against the forces of chaos.
One possible plot could be Percy struggling with the duality of his parentage. He might face discrimination from both the children of Hades and Poseidon. For example, the children of Poseidon could see him as a threat because of his connection to Hades, and vice versa. He could then go on a journey to prove that his dual heritage doesn't define him, but rather gives him unique powers to protect the world of the gods and mortals.
In this fanfiction, Percy might be in a situation where the relationship between Hades and Poseidon deteriorates due to some misunderstanding. As their son, he feels the need to reconcile them. He travels between the Underworld and the Seas, facing various trials in each realm. His powers from both parents are constantly put to the test as he tries to communicate with his fathers and make them see reason. In the end, his efforts not only mend their relationship but also strengthen his own place in the demigod world.
One great fanfiction idea could be a story where Zeus, Poseidon and Hades have to team up to face a common threat that is even more powerful than them. Maybe a primordial being awakens and they must put aside their differences. In this story, Percy could be the mediator between them, using his unique position as the son of Poseidon to try and keep the peace among the three powerful gods.
In a fanfiction where Percy is the son of Hades and Poseidon, his powers would be truly extraordinary. He could have the ability to create portals in water that lead to the Underworld. This would give him an advantage in both battle and travel. His hydrokinesis could be tainted with the essence of death, so when he attacks with water, it could cause a draining effect on his opponents, sapping their life force. Additionally, he might be able to sense the presence of the dead in any water source, which could be used for both reconnaissance and protection.
One possible plot twist could be that Percy, as the son of Hades and Hera, discovers a hidden power within him that can control both the underworld and the aspects of Hera's domain like marriage and family. This power could put him in the middle of a great conflict between the gods who are jealous of his unique abilities.
One plot idea could be Percy's struggle to fit in. Since his parentage is so unique, he might not be fully accepted by either the children of Hades or those of Hestia. Another could be his discovery of new powers. Maybe he can control both the underworld flames (associated with Hades) and the hearth flames (from Hestia).
A fanfiction could be about a competition among Zeus, Poseidon and Hades, and Percy has to be the judge. The competition could be something like who can best help a small, struggling mortal town without using their full power. This would show a different side of the gods and also test Percy's ability to be fair and objective.
One possible plot could be Percy discovering his true parentage as the son of Amphitrite. He might struggle with his identity, as he has always known Poseidon as his father. This could lead to a journey of self - discovery where he has to learn about Amphitrite's powers and how they are now a part of him.
One possible plot could be Percy's struggle with his dual heritage. He might be conflicted between the gentle, love - associated nature of Aphrodite and the powerful, tempestuous nature of Poseidon. He could be an outcast among both the children of Aphrodite, who are often more focused on beauty and charm, and the children of Poseidon, who are known for their strength and connection to the sea. This internal struggle could form the basis of a great adventure as he tries to find his place in the world of demigods.
A great plot could revolve around Percy's role in the power dynamics among the gods. As the son of Hera and Poseidon, he has the potential to shift the balance. Some gods might try to use him as a pawn, while others see him as a threat. Percy would then have to navigate this complex political situation among the gods while also dealing with his own personal growth and the challenges that come with being a demigod.
Maybe Percy discovers that there is a conspiracy within the Underworld to overthrow Hades. As the champion, he has to uncover the truth and stop the plot. Along the way, he meets old enemies who now see him as an ally of Hades and try to take advantage of the situation.
Well, Percy could start to resent Poseidon and all things related to him. He might decide to leave Camp Half - Blood and try to make it on his own in the mortal world. But then he realizes that his demigod powers still draw trouble, and he has to find a new way to deal with it without relying on his father's name.