Well, a plot could involve Percy being sent on a special mission by the Fates. Since they control destiny, this mission might be crucial for the balance of the entire demigod world. He could have to face enemies that are normally out of reach for regular demigods. Along the way, he discovers secrets about his adoption that change his perspective on his life and his role among his peers.
One idea could be Percy going on a quest that was pre - ordained by the Fates. He discovers that his every move is part of a larger plan they have for the demigod world. For example, he might be sent to retrieve an ancient artifact that holds the key to maintaining the balance between the gods and the Titans, and along the way, he has to face challenges that test his loyalty to the Fates' plan.
One idea could be Percy having to deal with the stigma of being associated with Hades in the demigod world. He might face distrust from other demigods who are scared of Hades' reputation.
One idea could be Percy having to learn the ways of Artemis's hunters. He might struggle with the no - male - contact rule at first but then find unique ways to bond with his new sisters. Another could be Percy going on a quest specifically related to Artemis's domain, like protecting a sacred forest. And he could use his water powers in new and unexpected ways in the context of Artemis - related tasks.
One idea could be Percy struggling with the dark influence of Kronos while still trying to maintain his loyalty to his friends at Camp Half - Blood. Another could be Percy having to hide his true identity as Kronos' adopted son from his closest allies. Maybe he discovers some long - lost powers or knowledge that Kronos had hidden away for him, which he must use to either save or destroy the world of the gods.
One idea could be Percy exploring his new powers related to Demeter. Maybe he can control plant growth in unique ways, like making plants form protective barriers. Another could be his interactions with Demeter's other children. He might face some jealousy from them at first but then prove himself and form strong bonds.
One idea could be Percy's struggle with his new identity as Nyx's adopted son. He might face discrimination from some of the other demigods who are suspicious of his new connection. Another plot could involve Percy learning new powers from Nyx that set him apart in battles against monsters. He could also have to deal with Nyx's enemies who target him because of his relation to her.
One idea could be Percy struggling to fit in with Athena's children at first. Since he's used to being a son of Poseidon, he has different ways of thinking and acting. Another plot could involve him using his newfound Athena - given wisdom to solve a really complex mystery in the demigod world. Maybe he discovers a new prophecy related to Athena that only he can understand because of his unique position as her adopted son.
One idea could be Percy having to learn the unique skills of Hephaestus' cabin, like forging magical weapons. He might struggle at first because he's used to his own powers. Another could be him having to deal with the other Hephaestus kids who are initially jealous of his fame as Percy Jackson but then come to accept him. And he could go on a quest where his new skills as an adopted son of Hephaestus are crucial in defeating a powerful monster.
Well, a plot idea could involve Percy being cursed by the fates to forget his own identity. He then has to go on a journey to rediscover who he is while still fulfilling his duties as the champion of the fates. Along the way, he might meet old friends who don't recognize him at first, and he has to prove himself to them. Or perhaps the fates send Percy on a mission to prevent a prophecy from coming true that would destroy the entire demigod world. This would involve him traveling to different mythological places and facing powerful enemies.
Maybe Percy is chosen by the Fates to be their champion in a battle against an ancient evil that threatens to disrupt the very fabric of fate. He has to team up with some unlikely allies, like minor gods who are also concerned about the balance of fate. He would have to learn new skills and face challenges that test his limits.