Well, perhaps it's a sleek, form - fitting armor that has the ability to change its appearance based on Percy's needs. It might start as a simple chainmail but when he's in danger, it could transform into a full - body plate armor with glowing blue accents that represent his powers. The new armor could also be enchanted to make him faster in water and more resistant to fire, which would be really useful considering the various challenges he faces in the Percy Jackson universe.
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.
In such fanfictions, Percy's character is often explored through his resilience. For example, if he's physically abused, we see how he still tries to fight back or find a way to escape, which shows his determination. His loyalty also comes into play as he might not want to burden his friends with what he's going through.
One possible fanfiction could be about Percy Jackson exploring the hidden magical corners of New York that are related to the concept of 'echo'. Maybe he discovers an ancient artifact in an alleyway that when touched, releases an echo of a past demigod's adventure. This could lead him on a new quest to figure out what the echo means and how it relates to the current threats against the demigod community in New York.
One idea could be that the new girl is a demigod from a very rare and powerful lineage. For example, she could be a descendant of a primordial god that no one has seen in centuries. This would bring a whole new dynamic to Camp Half - Blood as everyone tries to figure out her powers and where she fits in.
Some of the gods can also be common characters. For instance, Poseidon, Percy's father. He might play a role in either helping or hindering Percy's revenge, depending on the plot. Zeus could also be involved if Percy's revenge somehow crosses paths with the affairs of the sky god. And then there are the other demigods at Camp Half - Blood who could join Percy in his quest for revenge or oppose him if they have different views.
It could be that Percy's relationship with a certain god or goddess goes horribly wrong. Say he offends Aphrodite in a way that she convinces the other gods to disown him. Percy then has to struggle not only with the loss of his divine family but also with the isolation from the demigod community that follows such a disownment.
One interesting plotline could be Percy seeking revenge on a new enemy who has wronged his friends at Camp Half - Blood. Maybe this enemy has been stealing magical artifacts from the camp, and Percy decides to use his water powers and his wits to track them down and make them pay.
If Percy Jackson is sent to Tartarus in fanfiction, it could be a harrowing experience. First off, the environment itself is a nightmare. The terrain is dangerous and full of pits and lava. Percy would have to rely on his wits as much as his strength. Since Tartarus is the prison for the most powerful Titans and monsters, he'd be up against foes far more powerful than he's used to. He might even discover some long - lost secrets about his powers or his family's past while trying to find a way out.