Well, Percy might gain new powers related to the Underworld. Since Hades is the god of the Underworld, he could teach Percy how to control shadows or communicate with the dead. This would make Percy an even more formidable demigod, with abilities that no one else has. He could also face a lot of challenges from other gods who might be jealous or scared of his new connection to Hades.
His character would likely become more brooding. Being in the presence of Hades, who has a rather dark and serious nature, Percy might pick up some of those traits. He could be more introspective and less impulsive compared to when he was under Poseidon's influence.
Well, one thing that could happen is that Hermione would be exposed to a whole new family dynamic. Sirius has his own wild past and rebellious nature. He might encourage Hermione to be more daring in her magic, perhaps showing her some spells that are a bit on the edgy side but still within the bounds of good magic. Also, she could learn a great deal about the Marauders from him directly, which would give her a new perspective on the history of Hogwarts.
One interesting plot twist could be Percy finding out he has a hidden power related to Hades' realm that he didn't know about before. Maybe he can control a special type of underworld creature that no one has ever seen. Another could be Percy having to face off against a false heir to Hades' throne who is trying to frame him for crimes in the underworld.
Some of the more malevolent spirits or monsters from the Underworld could also be antagonists. They might resent Percy for being Hades' adopted son and try to undermine him. For example, a powerful undead general who believes he should be the one favored by Hades instead of Percy.
In such a fanfiction, Percy might help Hades with some internal underworld issues. For example, dealing with rebellious spirits. Since they are friends, Percy could use his unique abilities and knowledge of the modern world to assist Hades in modernizing certain underworld operations, like record - keeping. It could also lead to interesting interactions with other underworld deities who might be suspicious of this new friendship.
In this fanfiction, Percy could be exposed to different realms and dimensions that are part of Chaos' domain. He might meet some very strange and powerful creatures. Maybe he'll form alliances with them or learn from them to become an even greater hero. Also, his personality could change as he adapts to this new and wild environment under Chaos' care.
Well, in such a fanfiction, Percy would likely gain access to Batman's high - tech resources. He could use Batman's gadgets in his battles against monsters. Maybe Batman would train him in combat and detective skills, making Percy an even more formidable demigod.
In this kind of fanfiction, Percy might gain new powers or a different status. Hera could train him in her own ways, perhaps teaching him more about the divine politics and how to navigate the complex relationships among the gods. He may also have access to resources and knowledge that he didn't have before, which could change his future adventures drastically.
One possibility is that Percy's relationship with the other demigods would change. Since he is now under the wing of Apollo and Artemis, some demigods might be jealous or curious. He could also become a sort of mediator between the two gods' followers. For example, if there were disputes between the Apollo - related campers and Artemis - related hunters, Percy could use his position to resolve them.
Well, Percy could use his water powers in really cool ways during Avengers' battles. For example, he might create huge tidal waves to stop enemy attacks. And he could teach the Avengers some new combat moves that he learned from Camp Half - Blood. Maybe he'd also introduce them to Greek mythology monsters and how to fight them.