Percy could have different powers. Instead of just his water - based powers from being a son of Poseidon, as the son of Pluto, he could have powers like shadow manipulation. He could use these powers to move stealthily through the Underworld or even on the surface when in need. Also, his personality could be more solitary. He might not be as quick to trust others as the original Percy, given the more mysterious and often feared nature of Pluto.
He could be more brooding. Since Pluto is associated with the Underworld, Percy could have a darker, more introspective side. He might spend a lot of time thinking about the nature of death and the afterlife.
She could be more in tune with her femininity, using it as a strength rather than a hindrance. For example, she might be more perceptive about emotions, both her own and others', which could help her in diplomatic situations with the gods. Instead of the more straightforward and sometimes brash approach of the original Percy, Fem Percy could be more subtle and strategic.
One way to develop Percy is through his interactions with other characters. He could have confrontations with demigods who are suspicious of him. These interactions can force him to defend his existence and his right to be at Camp Half - Blood. At the same time, he could also have positive interactions with those who are more open - minded. This will show his ability to handle different types of relationships and grow as a character.
In fanfiction, their characters might be developed with more emotional depth. For instance, Percy could be shown to be more vulnerable about his feelings for Annabeth. Maybe he has nightmares about losing her and this makes him more protective in a different way than in the original. He might be more open about his fears, which wasn't really explored as much in the original.
In these fanfictions, Percy's character is often more edgy. He has to be more calculating and less impulsive compared to his original self. Since he's dealing with the assassin - like role, he can't just rush into things. For example, he might take more time to plan his attacks against enemies.
You can start by focusing on his internal conflict. Since Fenrir is a complex and often - feared figure, Percy would have a lot of self - doubt. He could question whether he's destined to be bad like his father is often portrayed.
Percy would probably become more arrogant at first. But as he faces challenges related to his new identity, he'd learn humility. His loyalty to his friends might be tested as Zeus could demand things that conflict with his friends' interests. He'd also have to deal with the expectations of being the son of the king of the gods, which would shape his character in ways different from when he was just Poseidon's son.
Percy would likely become more regal and proud. Since Hera is associated with royalty, he might develop a more refined and authoritative personality. He could also become more calculating, as Hera is known for her scheming. For example, he might think more about long - term plans rather than just reacting impulsively like he used to.
Percy's self - identity would be completely shaken. He's always known himself as Poseidon's son, so being a son of Ares would force him to re - evaluate who he is. He might struggle with feelings of anger and a desire for power that he didn't have before. This could lead to a darker path for him at first, but through various experiences, he could learn to control these new aspects of himself and become a more complex and interesting character.
She could be developed as more carefree compared to Percy. Percy is often uptight and by - the - book. His twin sister could be the one who's always breaking the rules in a harmless way, like sneaking out to the Forbidden Forest just to explore. This would make her a more rebellious character, which is a big contrast to Percy.
Developing his powers further is also a way. Since he's the son of Nyx, he could learn to manipulate different aspects of darkness like creating illusions using shadows or traveling through the dark realms faster. This would not only make him more powerful but also show his growth as a character as he masters these new abilities.