One idea could be that the OC is a new camper at Camp Half - Blood. She has a special power that Percy is intrigued by. They start off as friends, helping each other in various quests. As time goes on, they realize their feelings for each other during a particularly dangerous quest where they have to rely on each other completely.
Maybe the OC is from a different mythology background, like Norse. She comes to Camp Half - Blood seeking refuge. Percy is assigned to show her around. They initially clash due to their different beliefs and ways of doing things. But as they face common enemies, like monsters that target both Greek and Norse descendants, they grow closer and fall in love. The OC could introduce Percy to some unique Norse magic which helps them in battles.
Another plot could involve an OC who is a child of a minor god that has been overlooked by the Camp Half - Blood community. This OC, with Percy's help, tries to prove the importance of their godly heritage and ends up uncovering a long - lost prophecy related to their parent god. This would lead to an adventure full of self - discovery and challenges for both the OC and Percy.
One interesting plot idea could be her struggling with the stigma associated with being Hades' daughter. For example, other demigods might be scared or distrustful of her at first. Another could be her going on a quest related to the Underworld, like trying to stop some escaped souls from causing chaos on Earth. She could also have a special power related to the dead that she has to learn to control, such as being able to see the last moments of a dead person's life, which could be both a gift and a curse as she might see some really traumatic things.
A possible plot for this fanfiction could be that the Son of Thor is on a quest to retrieve a powerful artifact that has been lost in the world of Percy Jackson. Along the way, he teams up with various characters. He might have to deal with the cultural differences between the Norse and Greek ways. For example, the way they approach magic or combat. His interactions with other demigods could be filled with misunderstandings at first, but as they journey together, they come to understand and rely on each other. This could also lead to some interesting crossovers in powers and strategies.
A possible plot is that the reborn female OC starts to form a different kind of relationship with the existing characters. Since she's female, her friendship with Annabeth could be more of a sisterly bond where they support each other in different ways compared to Percy and Annabeth's relationship. And she might have a romantic sub - plot with a new character, someone who was not really in the spotlight in the original series. This new relationship could be shaped by her unique identity as a reborn character.
One idea could be that the fem oc is a new camper at Camp Half - Blood with a unique power related to nature. She and Percy have to go on a quest together to save a forest that is being poisoned by a mysterious force. Along the way, they discover that their powers work better together and start to develop feelings for each other.
A great plot could also involve the OC forming an unlikely alliance. He could team up with some of Percy Jackson's friends, like Annabeth. They initially don't trust him, but as they face challenges together, they realize that he's not like his father. This alliance could lead to them facing off against an ancient evil that only the combined knowledge and powers of the OC and the other demigods can defeat.
One idea could be that the male OC was a great hero in a past life. In his reincarnation, he starts having strange dreams about his past deeds. As he gets closer to the world of Percy Jackson, he discovers that his past life has some connection to an ancient prophecy that only he can fulfill. Maybe he has some latent powers from his past that start to emerge, like the ability to control a unique element that was thought to be lost in time.
One idea could be Percy discovers a new, forgotten power related to his 'son of love' aspect. Maybe he can heal emotional wounds of other demigods. For example, he helps a demigod who has been traumatized by past battles by using this power.
One plot idea could be that Percy, in his adventures, discovers a long - lost prophecy related to Athena. As he delves deeper into understanding it, he starts to develop a new - found respect and a kind of platonic love for Athena. He might see her not just as a goddess but as a key figure in the fate of the world and their relationship could be based on mutual understanding of the greater good.
Well, perhaps there could be a plot where an old, forgotten magic related to love potions resurfaces. Percy discovers a vial of this ancient love potion while on a quest. When he brings it back to camp, it accidentally gets spilled near a group of demigods. This causes a chain reaction of unexpected love interests. Some demigods start to form relationships they never would have considered before. It could also be used by an enemy who infiltrates the camp to use the chaos of the love - stricken demigods to their advantage, like stealing important artifacts while everyone is distracted by their new - found loves.