His character would change in many ways. Firstly, he'd gain a new sense of discipline. Athena is all about order and structure, and Percy would have to adapt to that. He might start to see the value in rules and planning. His sense of humor would also change a bit. He'd still be funny, but his jokes might be more intellectual or based on historical references. His leadership style would transform as well. Instead of leading with brute strength like he did as a son of Poseidon, he would lead with his wits and wisdom, inspiring others with his newfound knowledge and strategic thinking.
Percy would likely become more studious. Since Athena values knowledge, he would be more interested in learning about history, magic, and other aspects of the demigod world. He might spend more time in the library at Camp Half - Blood, much to the surprise of his friends. His relationships with others would also change. He could be more aloof at first as he tries to adapt to his new role, but as he grows into it, he would form deeper, more intellectual connections with those around him.
Percy would likely become more nurturing. Since Hestia is associated with the hearth and home, Percy might pick up her values of warmth and care. He could be more empathetic towards others, especially those who are homesick or lost. For example, he might be more patient with new demigods arriving at camp.
His character would develop in multiple ways. Firstly, Percy would gain a new sense of discipline. Hephaestus' work demands it. He'd have to follow strict procedures when forging. This would contrast with his more impulsive nature. He'd also develop a new kind of confidence. Knowing he can create things gives him a different kind of power. And he'd probably become more of a team player within the Hephaestus cabin. He'd learn to collaborate with the other kids, sharing ideas and skills. He'd start to understand that his success isn't just about his own abilities but also about how well he can work with others in this new area of expertise. Overall, he'd transform from a mostly solo fighter to someone who can contribute in a group setting in a whole new way.
Percy would likely become more in tune with the arts and creativity. As Dionysus is associated with theater and celebration, Percy might start to appreciate and participate in these aspects more. He could become more flamboyant in his expressions and actions, which is a contrast to his more straightforward nature as a son of Poseidon. For example, he might start to use his powers in more creative ways during battles, like creating illusions of vines and grapes to confuse his enemies.
He'd probably be more aware of his appearance. Instead of just being a scruffy, normal - looking demigod, he might take more care in how he presents himself. He could also be more charming without really trying, which might get him into trouble sometimes as people might misinterpret his intentions.
Percy would likely become more conflicted. His previous identity as the son of Poseidon shaped his values and actions. But as the son of Kronos and Rhea, he'd have to reevaluate everything. He might become more cautious, as he now represents a more controversial lineage.
With the other demigods, Percy could become an outcast at first. They might see his adoption by Erebus as something unnatural or dangerous. But as time goes on, if Percy uses his new powers and influence for good, he could gradually regain their trust and respect. For example, he could use his shadow - related abilities to help in battles or rescue missions, showing that he's still on their side.
Percy would likely become more devious. Growing up with Loki as an adoptive father, he'd be exposed to Loki's tricks and lies. So instead of his straightforward, if sometimes impulsive, nature in the original Percy Jackson stories, he might think more about the different angles of a situation before acting.
His relationship with Annabeth would change. She might be a bit jealous at first of Percy's new connection to Hecate. But then she would see how his new powers could be useful. They would have to learn to work together in a new way, with Percy having different abilities to bring to the table. His friendships with other demigods like Grover would also be different. Grover might be a bit in awe of Percy's new magical side. Percy would also have to form new relationships with the followers of Hecate, who might be very different from the demigods he's used to.
When it comes to his relationship with Hera herself, it would be complex. At first, Percy might be resentful or confused about being adopted by her. But as time goes on, he might start to understand her in a way no one else does. Hera could start to see Percy as a true son, and this could lead to a deep, if somewhat unusual, bond between them. Percy would have to balance this new relationship with his existing ones, and it could lead to some really interesting character development and story arcs.
Percy's relationship with the male demigods would change significantly. Some might see him as a traitor for joining the Hunters. However, he would also gain new allies among the Hunters themselves. His relationship with Artemis would be that of a mentee and mentor at first, but as time goes on, it could develop into a more family - like bond. And his relationship with the gods would be different too, as he's now under Artemis's protection, which might make some gods view him in a new light.