His dad might be initially shocked but quickly become accepting. After all, he is a god and has seen many strange things. He would probably use his power to make Percy's life easier during the transition, like providing resources or protection.
There's also 'Poseidon's Promise'. This fanfic delves into how Poseidon made a secret promise to protect Percy in a way that goes beyond the normal godly duties. It has some really cool action scenes where Poseidon uses his powers to fend off threats to Percy. It's a great read for fans who want to see more of Poseidon's protective side.
In some Percy Jackson fanfiction, Piper's dad is often portrayed as a complex figure. He might be shown as a strict but loving father. He could be a source of strength for Piper, especially when she's facing the challenges in the demigod world. His mortal side might be emphasized, making his relationship with Piper a bit of a struggle as she navigates her divine heritage.
Well, sometimes in fanfiction, his brother might be a mortal who discovers his demigod heritage later. This could add an interesting twist to the story as he has to adapt to the world of gods and monsters. Or it could be a long - lost half - brother from a different camp, like a son of Poseidon from another part of the world who was hidden away for some reason.
Often, he plays the role of the grounding force in Piper's life. Since Piper is involved in the crazy world of demigods, her dad represents the normal, mortal part of her life. He can be a reminder of the world she has to protect.
Another theme is the over - protective father. In these fanfictions, Poseidon is extremely protective of Percy. He might go to great lengths to keep Percy out of danger, even if it means going against the other gods. This often leads to some tense moments between Poseidon and the other Olympians, and also shows the depth of his love for Percy.
Annabeth Chase would most likely be one of his allies. She has always been by Percy's side, and she shares his sense of justice. If Percy decides to take on the gods, she would be there to support him with her intelligence and strategic thinking.
Some minor gods related to the earth like Demeter could be allies. She has her own powers over the earth and could teach Percy some of her techniques. Also, the nymphs, such as the water nymphs and the tree nymphs, could be allies. The water nymphs could help with the water sources within the earth (like underground rivers) and the tree nymphs could help Percy take care of the forests. And let's not forget the pegasi. They could be used for transportation when Percy needs to quickly travel across his earthly domain.
Annabeth could definitely be one of his main allies. Her intelligence and strategic planning would be invaluable in a fight against Olympus. Also, Grover might be there, using his skills as a satyr to gather information and support from other nature - related beings. Some of the less - well - known demigods from Camp Half - Blood could also join in, seeing Percy as a chance for a new order.
Annabeth could definitely be one of his allies. She's smart and resourceful, and her knowledge of architecture and strategy would be useful no matter where in the universe they are. She could help Percy figure out the layout of strange alien cities or fortresses.