Perhaps it's a story about them adapting to life on Olympus. Thalia could be training the young demigods there, Nico might be exploring the more mysterious parts of Olympus that are related to the Underworld, and Percy could be dealing with the politics of the place. It could be full of adventures as they face challenges from both the gods and other creatures.
In this fanfiction, they could be living on Olympus as a sort of reward for their great deeds. Percy, with his heroic acts, Thalia for her leadership, and Nico for his contributions to the demigod world. Their presence on Olympus could disrupt the normal order at first, but then they start to make positive changes. For example, Percy might introduce new ways of using water power for the benefit of all on Olympus, while Thalia and Nico bring in their own unique perspectives and skills.
Well, one possibility could be that they are given special status on Olympus. Maybe they are tasked with keeping the peace among the gods, which would lead to a lot of interesting interactions with the deities. They might also use their unique powers to improve the living conditions on Olympus, like Percy controlling water to create beautiful fountains or something.
It could be some of the jealous gods. Since Percy, Thalia, and Nico are living on Olympus, which is quite an unusual thing for demigods, some gods might not like their presence and try to get rid of them. For example, a god who feels that their power is being threatened by these demigods.
A possible plot twist could be that one of them is actually a secret weapon of an enemy god. For example, Nico could be unknowingly influenced by a dark force that wants to use his powers to bring chaos to Olympus.
The fanfiction could also focus on their relationships. Percy, Thalia, and Nico might form a very tight - knit group, almost like a family. They would have to rely on each other in the often - cutthroat environment of Olympus. Their friendships could be tested as they grow older and face different challenges. For instance, Percy might be offered a high position in Poseidon's court that would take him away from his friends. Thalia could be given responsibilities that conflict with her loyalty to her friends. Nico might struggle with his identity as he tries to fit in on Olympus while still maintaining his connection to the Underworld.
Perhaps it's a fanfiction focused on their relationships. They might form an unexpected bond in the story. Nico, who has often been a bit of an outcast, could find real friendship and acceptance from Percy and Thalia. They could start out on a simple quest, like finding a lost artifact, and during this journey, they learn more about each other and grow closer as friends.
The fanfiction could explore their relationships with the gods. Since they are born on Olympus, the gods might take a special interest in them. For example, Poseidon could be even more protective of Percy, Zeus might keep a closer eye on Thalia, and Hades could have different plans for Nico. Their story could be about how they navigate these complex relationships while also trying to find their own identities. They might face jealousy from other demigods who are not born on Olympus, and have to prove themselves worthy not just because of their birthplace but also through their own deeds.
It could be about their unique upbringing on Olympus. Maybe they have to deal with the politics among the gods while growing up. For example, Percy might struggle with Poseidon's expectations and his own identity in this divine setting. Jason could be learning about his Roman heritage in a more Greek - influenced environment. And Nico might be trying to find his place among the living and the dead while being raised on Olympus.
It could be that they run away to find someone. Maybe a missing demigod friend or a powerful being who can help them with a problem they're facing. Percy, Thalia, and Nico might have received a mysterious message or a vision that leads them on this journey. As they run away and start their search, they encounter various obstacles. They have to cross dangerous terrains, deal with unfriendly gods or demigods who don't want them to succeed, and also figure out how to work together effectively. Their friendship is tested, but in the end, they grow stronger together.
Percy could develop a more god - like sense of responsibility. Growing up on Olympus, he would be constantly exposed to the grandeur and the weight of the gods' duties. Thalia might become more confident in her leadership abilities as she is among the most powerful beings from the start. Nico could overcome his shyness faster as he is used to the presence of the gods. He would be more assertive in using his powers.
They could be like siblings. Percy and Thalia might act as the older siblings, protecting and guiding Nico. Percy, with his leadership skills, and Thalia, with her combat abilities, would be great at looking out for the younger Nico. They could also be like cousins, with a close - knit bond but still having their own individual family heritages that sometimes create interesting dynamics.
One challenge is the jealousy of other gods. Since they are new gods, the older, more established gods might not like the attention they get or the new ideas they bring. Another challenge is controlling their powers. As mentioned before, going from demigod to god means a huge jump in power level, and it's not easy to get used to. For example, Percy might accidentally flood a city while trying to create a small puddle for fun.