A possible plot could be that Percy and his mom are transported to an alternate version of their world. In this world, the rules of magic are different, and they have to quickly adapt. Percy's mom uses her knowledge of the normal world and her maternal instincts to keep them alive, while Percy uses his combat skills. Together, they try to find a way back home and in the process, they form an even stronger bond.
Well, in some percy and his mom fanfiction, there might be a plot where Percy's mom gets kidnapped by an old enemy. Percy then has to go on a solo quest to rescue her, facing many challenges along the way. He might have to use his skills and the help of some new friends he makes during the journey. And along the journey, he also discovers some long - lost secrets about his family.
One interesting plot could be Percy and his mom going on a magical adventure together. Maybe they discover a hidden realm full of strange creatures and have to use their wits to get out. Another could be Percy's mom getting some sort of special power and they team up to fight against a new threat in the Percy Jackson universe.
A plot could revolve around a mystery that they need to solve. They might start as strangers but gradually become partners in the investigation, uncovering secrets about their world along the way.
Grover could be a popular character. Since he's Percy's best friend, he might be involved in the fanfiction, perhaps helping Percy protect his mom or going on adventures with them. Another could be Annabeth. Her intelligence and skills could be useful in the stories, like when they are facing a difficult situation and she comes up with a clever plan.
One interesting plot could be Percy having to prove himself to Poseidon in a new and unexpected way. For example, he might have to solve a mystery that is directly related to Poseidon's power over the sea but in a realm that is unfamiliar to both of them, like an underwater civilization that has been lost for centuries.
One possible interesting plot could be Percy's struggle with immortality. He might face the loneliness of outliving his friends and loved ones. Another could be how he uses his immortality to protect the world in new and different ways, perhaps by being able to take more risks without the fear of death.
Well, perhaps Percy discovers a hidden magic within himself that he didn't know he had. Maybe he starts off struggling with basic spells and then gradually masters more complex ones. For example, he could be trying to make objects levitate at first and later on be able to conjure powerful shields.
Another plot could involve the Earthshaker being awakened accidentally. This causes chaos not only on Earth but also in the Underworld. Percy and his companions need to travel to different realms, including the Underworld, to figure out how to put the Earthshaker back to sleep. They encounter different gods and goddesses during their quest, and some might help while others might try to hinder them.
One interesting plot could be Percy's journey to regain his lost status among the gods. Maybe he has to complete a series of dangerous quests that test his powers and loyalty. Another could be Percy forming an unlikely alliance with other forgotten or outcast deities to rise up against the more dominant gods who have pushed him aside.
One possible interesting plot could be Percy's struggle to adapt to his new status as a banished god. He might have to deal with the loss of his former powers and the isolation from his old world.
A cool plot could be a time - travel fanfiction. The Minotaur travels back in time to the era when the gods were more actively involved in the mortal world. He could interact with the gods, and Percy has to follow him through time to stop him from causing chaos. This would involve Percy having to deal with different rules and powers in the past, and also understanding the Minotaur's motives for going back in time.
One interesting plot could be where the NPU (assuming it's some new power or entity in the Percy Jackson universe) is a key to unlocking an ancient prophecy that no one knew existed. Percy and his friends have to figure out how to use the NPU to their advantage while also dealing with the usual monsters and gods trying to stop them.