Give her some flaws as well. For instance, she might be a bit over - confident at times. She thinks she can handle a certain situation on her own but actually gets into trouble. This flaw can lead to her learning important lessons. And in the fanfiction, you can show how she grows from these experiences. Maybe she starts to listen more to the advice of others and becomes more cautious while still maintaining her adventurous spirit.
You can start by giving her a distinct personality. Maybe she's really shy but has a fierce determination inside. For example, she might be quiet in group settings but when it comes to protecting her friends or family, she's fearless. Give her some hobbies too, like she loves to draw the different mythical creatures she's heard about. This can show her creativity and her connection to the world of the gods.
She might start off as a shy character. But as the fanfiction progresses and she discovers her connection to lemons, she becomes more confident. For example, if she uses lemons to make a magical item, she realizes her own capabilities and starts to stand up for herself more.
Give her a distinct personality. For example, she could be really curious, always asking questions about the demigod world. Make her brave but also a bit naive at times. She might be more in tune with nature than other characters, able to sense things about the environment. Another aspect is to show her relationship with Percy. She could look up to him and want to be just like him, but also have her own ideas about how to handle situations.
For Percy, you can show his protective side more when it comes to his sister. Have him be more cautious and less reckless in situations where her safety is at stake.
His character would become more confident in his artistic abilities. Apollo is the god of many arts, so Percy would likely be exposed to music, poetry, and painting. He might be more flamboyant in his actions and speech, as Apollo has a certain charm. For example, he could start using more flowery language when talking to his friends or enemies.
Percy's character would likely become more in tune with nature. He'd be more reserved perhaps, as he grows up in an all - female group. His sense of honor might be more shaped by Artemis' values, such as protecting the weak and the natural world.
You can start by giving her a distinct personality. For example, if Percy is brave and impulsive, she could be more cautious and analytical. Show her interests, like if she loves art or is into science. Also, explore her relationship with Percy. Maybe she's a bit jealous of all the attention he gets, but also proud of him. Another aspect is her reaction to the demigod world. She could be initially skeptical and then gradually accept it.
Percy's character development in this fanfiction might start with a sense of loss. Losing his demigod status means losing a big part of his identity. He may become more humble as he realizes the challenges that mortals face every day. As he adapts to mortal life, he could become more self - reliant in different ways, like having to earn money for the first time or deal with normal school problems without relying on his powers.
In the fanfiction, their relationship could start off rocky. Maybe the sister resents Percy for always being in the spotlight. However, as they face challenges together, like fighting a powerful monster, they start to understand each other better. Percy learns to listen to his sister's ideas, and she learns to trust his experience. Eventually, they become a great team and have a really close relationship full of mutual respect.
Percy's character would be very different. Growing up alone, he would lack the social skills he has in the original series. He'd be more introverted. His view of the gods would be more cynical as he has no one to tell him the 'glorified' stories. He'd have to learn about his powers through trial and error, which would make him more cautious. He may also develop a stronger survival instinct. His relationships would be different too. He might be more hesitant to open up to others when he finally does meet people. Overall, his character would be a loner with a unique perspective on the demigod world.
In many fanfictions where Percy becomes the God of the Universe, his character often develops a more profound sense of responsibility. He starts to see the bigger picture of the cosmos. For example, he might become more detached from his former mortal relationships as he has to deal with the grandeur of the universe. His power also changes his perspective. He may start to view the various pantheons differently, not just as separate entities but as parts of a greater whole that he now oversees.