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.
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.
Well, having wings could make Percy more independent. He can now reach places on his own without relying on his friends as much. This might cause some tension in his relationships at first, but it also forces him to grow and learn how to balance his new independence with his need for his friends. For example, he might fly off to scout ahead during a quest and have to make quick decisions on his own, which is a big step in his character development.
I don't know for sure as I haven't read this particular fanfiction. It could feature Percy Jackson himself, or maybe some of the other well - known characters from the series like Annabeth or Grover.
Percy might meet an old enemy who has somehow been resurrected or changed in the future. This enemy could be more powerful and have a new plan to take over the world or destroy the demigods. Or he could meet a group of time - traveling demigods from an even further future who are trying to fix something in Percy's future that has gone wrong.
There's a chance that it could be a character from Percy's family. For example, a distant relative who has been corrupted by some dark magic. They might betray Percy for their own gain or because they are being controlled, and this betrayal could lead to Percy being killed.
He might encounter new demigods who are also on the run or hiding from the traditional demigod society. These could be demigods with different powers or backgrounds that Percy has never seen before.
I'm not sure exactly as I haven't read it. But it might be about how love empowers the characters in the Percy Jackson universe, perhaps giving them the metaphorical 'wings' to overcome challenges or grow as individuals.
One interesting story could be about Percy using his wings to reach new and hidden places in the demigod world. Maybe he discovers a secret island where ancient monsters lurk. With his wings, he has an advantage in exploring and fighting them off.