Percy's power over water could potentially interact with Bastet's association with cats. For example, he could create water illusions of cats using his hydrokinesis. Bastet, on the other hand, might be able to enhance Percy's agility and stealth, like a cat, when he's in combat.
One plot idea could be Percy being transported to the Egyptian realm and encountering Bastet. He could be on a quest to retrieve an artifact that Bastet guards. Another could be Bastet choosing Percy as a champion to fight against an emerging evil in both the Greek and Egyptian mythologies. Maybe Percy has to learn Egyptian magic from Bastet to save his friends.
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.
It could be a fanfiction where the character Percy is placed in an Egyptian - inspired setting. Maybe Percy has adventures in the world of Egyptian mythology, interacting with Egyptian gods, facing challenges in the deserts or ancient temples.
A frequently seen theme is the exploration of new relationships. Percy forms alliances and rivalries with various Egyptian gods and demigods. Also, the theme of self - discovery is common. In these fanfictions, he often learns more about himself through his interactions with the Egyptian pantheon. For example, he might find out that he has hidden strengths or weaknesses related to the Egyptian magic or godly powers.
A plot could revolve around Percy being the only one who can stop an ancient curse that is affecting the descendants of Bastet. He has to search for the source of the curse, which leads him through different magical realms. Maybe Percy has to use his unique abilities, like enhanced speed and agility that come from being Bastet's son, to outwit the dark forces behind the curse. Also, he could form an alliance with other demigods from different pantheons to succeed in his mission.
Percy would interact in a cautious yet curious way. He'd be curious about their powers, like Anubis' role in the afterlife. But he'd also be cautious as he doesn't know how they'll react to a Greek demigod. He might use his charm, which has worked on some Greek gods, to try and build relationships. However, he may face some resistance from the more xenophobic Egyptian gods who see him as an intruder.
Ra, the sun god. Maybe the story is about Ra losing his power to make the sun rise, and Percy has to help him get it back. This could involve a journey through different realms, with Percy using his wits and Ra using his remaining divine knowledge to solve the mystery of what has happened to his power.
The fanfiction might involve Percy being a guide for an Egyptian god who is new to the mortal world. Percy shows the god how things work in this world, and they get into all sorts of adventures together. For example, they could be trying to stop a dark force that is threatening to disrupt the balance between the mortal and divine realms. And during this journey, the Egyptian god might use his unique powers and Percy his own skills to overcome the obstacles.
Percy, as the son of Bastet, would likely have powers related to feline - like abilities. For example, he might have enhanced speed, agility, and reflexes compared to other demigods. His senses, especially his sight and hearing, could be much sharper. Also, he could potentially have some sort of connection to cats, being able to communicate with them or understand their behavior in a way other demigods can't.