It could be a jealous demigod. Maybe someone who has always been envious of Percy's popularity and abilities. Now that Percy has wings, this demigod sees it as an opportunity to make Percy look bad. They spread rumors that Percy's wings are a sign of him being cursed by the gods and try to turn other demigods against him while he's already feeling sick and struggling with his new wings.
In this 'Percy Jackson Gets Wings' sick fanfic, it could be that Percy gets wings as a gift from an unknown god. But the wings come with a curse that makes him sick. He starts having visions whenever he tries to fly. These visions show him some dark secrets about the gods. Percy has to figure out what the visions mean and how to break the curse while also learning to control his new wings. He might go on a journey to consult the Oracle or some other wise beings in the demigod world.
Perhaps it's a gift from his father, Poseidon. Since Poseidon has control over the sea and all things related to water, he might have some connection to a power that gives Percy wings, like as a way to help Percy reach new heights both literally and metaphorically.
One possibility in this fanfiction is that the wings change Percy in some way. They might give him a new perspective, literally and figuratively. As he soars through the skies, he could see things he's never noticed before on the ground. This could lead to him discovering new secrets about the demigod world or even his own powers. He might also face new challenges, like dealing with air - based monsters or learning to fly in different weather conditions.
In the fanfic, it could be that Percy gets Triton as a gift from Poseidon. Triton could be initially reluctant to be with Percy, seeing him as an upstart half - blood. But as they spend time together, they start to understand each other better. Triton might help Percy improve his control over water, especially in more complex and powerful ways. They could go on quests together, like finding a lost ancient sea artifact that has the power to either save or destroy the world of the sea gods.
Annabeth would probably be very worried and take charge. She'd start researching immediately, looking through books in the camp library to find a cure. Grover would be constantly by Percy's side, using his nature - related powers to try and make Percy more comfortable, like bringing in fresh air and plants to help him feel better.
These fanfics can have a significant impact. They add new dimensions to the characters. For Percy, being sick shows his vulnerability, which is not always explored in the original books. It makes him more relatable to fans who have also experienced illness. Fans can then engage more deeply with the character.
In some Percy Jackson sick fanfics, the author might take a different approach. Instead of a physical illness, Percy could be affected by a mental or emotional 'sickness'. For example, he could be suffering from a curse that makes him lose his confidence or his sense of self. This would change his character dynamics as he would no longer be the fearless hero we know. His friends would have to find a way to break the curse and bring back the real Percy.
In a Percy Jackson fanfic with a sick Octavian, one possibility is that the sickness is some sort of magical or divine affliction. This could tie into the overall mythology of the series. For example, it could be a curse from an angry god because of something Octavian did. His struggle with the sickness could then be a journey of self - discovery and redemption. He might start to see the error of his ways, especially if he has to face his mortality. And this could have a ripple effect on the relationships between the demigods of the Greek and Roman camps.
Perhaps Octavian's sickness is a way for the author to explore themes of forgiveness and acceptance. He could be a really unlikable character at first, but as he gets sick, he starts to change. The other characters see this change and start to question their own prejudices against him. His sickness could be a catalyst for him to make amends with those he has wronged in the past. And the story could end with him either fully recovered and a changed person, or with his death being a turning point for the other characters to become better.