He could interact in a competitive way. Since his powers are likely to be strong due to his unique heritage, other demigods might see him as a rival. For example, in training sessions or during quests, Percy's abilities could outshine the others, leading to some jealousy and conflict. But over time, they could learn to work together and respect each other's strengths.
Percy might initially be an outcast among the other demigods. His parentage is quite different from the normal Olympian - related demigods. They might be wary of him because they don't understand his powers. However, some brave demigods could be curious and try to befriend him.
He would probably be a bit of an outcast at first. Since his parentage is so different, other demigods might be wary of him. But once they see his skills and powers, they would start to respect him. He might teach them some unique combat techniques he learned from his Titan mother Rhea, like different ways of using his powers in battle.
Perhaps Percy discovers a prophecy related to his birth. It could state that he is the key to either saving or destroying the world. This would create a lot of internal conflict for him. On one hand, he has his friends and the people he cares about in the mortal world. On the other hand, his powers and his role according to the prophecy could force him to make some very difficult choices.
In a more complex way, Percy's interactions could be influenced by the political situation between the Greek and Egyptian gods. If there's some sort of tension between the two pantheons, the demigods might be caught in the middle. Percy would have to be diplomatic and try to find ways to keep the peace while still maintaining his own beliefs and loyalties. For example, if there was a dispute over a powerful magical artifact, Percy and the Egyptian demigods would have to figure out how to resolve it without starting a full - blown war between their respective godly parents.
Developing his powers further is also a way. Since he's the son of Nyx, he could learn to manipulate different aspects of darkness like creating illusions using shadows or traveling through the dark realms faster. This would not only make him more powerful but also show his growth as a character as he masters these new abilities.
The Son of Anubis has powers related to the afterlife, like being able to sense when death is near or having some control over the souls of the dead. Percy, on the other hand, has his demigod strength and his ability to control water. If they were in a fight against an enemy that was immune to physical attacks, the Son of Anubis could use his powers to weaken the enemy's soul while Percy uses his water powers to create distractions or barriers. Their powers could also work in a complementary way in a more positive sense. For instance, if they were trying to heal a cursed place, the Son of Anubis could use his knowledge of the afterlife to identify the source of the curse, and Percy could use his water to cleanse the area.
Well, it could be about Percy having to deal with the powers and heritage that come with being the adopted son of Pontus. Maybe he discovers new underwater abilities that are different from his Poseidon - given powers. He might also have to face enemies who are after the secrets Pontus has.
Perhaps an ancient sea god who was once an enemy of Pontus. This god could see Percy as a threat because of his heritage. He would use his own minions, like sea serpents and murlocs, to attack Percy and those he cares about. He might also try to corrupt Percy, tempting him with power to turn against his friends.
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.
His powers would likely be much darker. He might have the ability to manipulate shadows like Nyx, using them to hide or even attack. And from Tartarus, he could have the power to cause earthquakes or open up chasms in the earth. He could also have a natural resistance to the harmful effects of the Underworld, such as the poisonous gases and the draining of energy that normal demigods experience.
His relationship with Annabeth would be very different. Annabeth might be initially scared of Percy because of his dark lineage. She would be cautious around him as she is used to the more 'typical' demigods. Percy, on the other hand, might feel isolated from her because he knows she is wary. His friendships with the other demigods at Camp Half - Blood would also change. Some might avoid him, while others might be intrigued by his new powers and origin. Grover, for example, might be torn between his loyalty to Percy and his fear of what Percy could become.