Well, they might lose trust in their friends. For example, if they were betrayed by someone they considered a close ally in the demigod world, like a fellow camper at Camp Half - Blood. Percy could become more withdrawn, as he has always been a bit of a loner at heart. Thalia might turn bitter and angry, using her skills as a hunter more aggressively. Nico, being the son of Hades, could potentially be pushed towards using his darker powers in retaliation, perhaps even seeking vengeance in the Underworld's way.
In a fanfiction where they go to high school, Percy would likely be popular for his heroic deeds and good looks. He might join the swim team and break all the records. Thalia could be the cool girl who rides a motorcycle to school and gets into trouble for parking it in the wrong place. Nico would be the mysterious new kid. There could be a plot where they have to team up to stop a monster that is lurking in the school basement.
In the fanfiction, they could be given important missions. Maybe they are tasked with restoring balance in a part of the Chaos realm that has been thrown into disorder. Percy's leadership skills, Thalia's combat experience, and Nico's knowledge of the underworld could all be put to good use. They would have to work together, which might not be easy at first given their different personalities. But as they face challenges, they would grow closer and become a more effective team.
They could be sent on epic quests by Chaos. Maybe they have to retrieve some powerful artifacts that were lost in the chaos of creation. Along the way, they would face numerous challenges and meet all kinds of strange creatures. Percy would use his strategic thinking, Nico his knowledge of the underworld, and Thalia her leadership skills to overcome obstacles and make their way towards their goal.
Well, they could be betrayed by someone they trusted deeply, like a fellow demigod. Maybe this person spreads false rumors about them, leading to their isolation within the demigod community. The three of them would then have to struggle to clear their names and find out who really set them up.
In a fanfiction about their betrayal, it could be that they are betrayed by a new character who infiltrates their group. This new character might seem friendly at first but then turns on them to further their own secret agenda, perhaps related to an ancient prophecy. Percy, Nico and Thalia would then have to figure out how to stop this new threat while also clearing their names.
One possible plotline could be that Percy, Thalia and Nico are betrayed by their closest friends within the demigod community. Maybe they are framed for a crime they didn't commit, like stealing a powerful artifact. This could lead to them being hunted by their own kind. They would then have to go on the run, trying to clear their names while also facing various monsters that are after them because of the false accusations.
In fanfiction, they might have an epic adventure. Percy could use his water powers to protect them if they encounter any danger. Thalia with her lightning might strike down foes. Nico could summon the dead to get information. Rhea might offer them some ancient wisdom or a special quest to save the world.
Perhaps it starts as a misunderstanding. Percy might misinterpret something Nico does as a threat to his friends. Thalia, being Percy's friend, jumps in to defend him. Nico, feeling attacked unjustly, then retaliates. It could turn into a full - on fight with them using their powers. Percy with his water - based powers, Thalia with her lightning, and Nico with his control over the dead. The fight could be a very intense and action - packed scene in the fanfic.
In this kind of fanfiction, they might face challenges adjusting to the new magical environment. Percy could be confused by the different types of magic in Hogwarts compared to his own demigod powers. Nico might struggle with the more structured and rule - bound nature of Hogwarts. Thalia could find it interesting but also be a bit rebellious against some of the Hogwarts traditions.
The camp leaders might betray them. If there is a power struggle within the camp, and Percy and Nico are seen as threats to the current leadership's power, the leaders could set them up. They could make it look like Percy and Nico are breaking camp rules or endangering the other campers, which would lead to the rest of the camp turning against them.