His personality could be more solitary. Hades is not exactly a social god, and Percy, being raised in that environment, might not be as eager to make friends or be part of a big group like he was in the original series. He might prefer to work alone and trust only a select few, as he has grown up in a more isolated and secretive world under Hades' care.
Percy might be more calculating. Hades is a shrewd god, and being raised by him, Percy would likely learn to think several steps ahead. He would be less impulsive in his actions compared to the original Percy. For example, when facing an enemy, he would take time to analyze their weaknesses rather than charging in headfirst.
He'd probably be more brooding. Growing up with Hades, he'd be exposed to the darker side of the mythological world constantly. So, instead of the somewhat upbeat Percy we know, he might be more withdrawn and moody.
His communication style could be different too. He might be more direct and simple in his speech, like how animals communicate basic needs and emotions. He wouldn't be as interested in the complex social hierarchies and politics among demigods. Instead, he'd focus on the more straightforward relationships based on mutual respect and survival, much like the relationships in the animal kingdom.
Percy's personality would be a far cry from the original. He'd be more secretive, for one. Growing up in the Underworld, he'd learn to keep his cards close to his chest. He'd also be more intimidating. His sense of humor might be darker, and he'd have a different moral compass. Instead of the typical heroic values, he'd have values more in line with the Underworld's survival - of - the - fittest mentality. He might be more distrustful of others and less likely to form quick alliances.
Percy's personality would be more in tune with nature. Since Artemis has a strong connection to nature, Percy would grow up respecting and understanding it more deeply. He would probably be more solitary as well, as the hunters often keep to themselves. He might not be as quick to trust others as he used to be, having been brought up in a more exclusive group. Also, he would have a greater sense of loyalty towards Artemis and the hunt, which could make him seem a bit cold to outsiders.
Percy could be more in tune with his emotions. Dionysus is associated with passion and ecstasy, so Percy might be more openly emotional, not suppressing his feelings as much as he did in the original stories. He could also be more creative, as Dionysus has an element of creativity in his domain. For example, he might be better at coming up with unique solutions to problems using his more artistic side.
Percy's character development would be different in several ways. Since Chiron is a centaur with vast knowledge and wisdom, Percy would be exposed to a deeper understanding of mythology and the history of the demigod world from a very young age. This could make him more cautious and less likely to jump into dangerous situations without thinking. He might also be more empathetic towards other mythical beings as Chiron would teach him about their natures and roles. Additionally, his relationship with the gods could be more complex. Instead of just being a hero who serves the gods' whims, he could have a more nuanced view and be able to question their actions based on what he has learned from Chiron.
Percy's personality would likely become more hardened. Growing up with assassins, he'd see a lot of violence and death. This would make him less trusting and more cynical. He might not be as quick to make friends as he was in the original story. However, his loyalty to those he does trust would be even stronger, like the loyalty assassins have to their comrades. Also, he'd be more disciplined, following the assassin code he was raised with.
Percy's personality would probably be more solitary at first. Growing up with wolves, he's used to relying on himself and his pack. So when he enters the world of demigods, he might have trouble trusting others immediately. He'd be more in tune with his instincts, which could make him seem unpredictable to those who don't understand his background. For example, he might follow his nose or gut feeling more often than following the advice of others.
Percy could have the power to manipulate the coldness that is often associated with the Underworld. He could freeze his opponents or create ice - like structures out of the cold energy. This would be different from his water - based powers in the normal story. Also, he may have a stronger connection to the gems and precious metals that are found in the Underworld, being able to sense them and even use them in some way for his benefit.
He'd likely be more reserved. Artemis values solitude and purity, so Percy might be less of a joker. He'd be more serious about his duties and tasks.
In a fanfiction where Percy is the son of Hades and Poseidon, his powers would be truly extraordinary. He could have the ability to create portals in water that lead to the Underworld. This would give him an advantage in both battle and travel. His hydrokinesis could be tainted with the essence of death, so when he attacks with water, it could cause a draining effect on his opponents, sapping their life force. Additionally, he might be able to sense the presence of the dead in any water source, which could be used for both reconnaissance and protection.