I'm not entirely sure as it could be about many things. It might be a fan - created story where Percy is portrayed as the son of Chaos. Maybe it involves Percy having special powers or going on unique adventures because of his relation to Chaos.
One possible plot could be Percy's struggle to balance his two powerful heritages. He might face challenges from both the forces of Chaos and the underwater world of Poseidon. For example, the denizens of the deep might be wary of his Chaos side, seeing it as a threat to their ordered underwater society. Meanwhile, the chaotic entities could try to pull him fully into their realm, away from his connection to Poseidon.
One interesting plotline could be Percy's journey in the realm of Chaos. He might face new and extremely powerful enemies that test his skills in ways not seen in the original series. For example, he could encounter primordial entities that are far more ancient and mysterious than the Titans or the Giants.
You could try looking on popular fanfic websites like Archive of Our Own (AO3) or FanFiction.net. They have a large collection of fan - created works and there's a good chance you'll find it there.
One possibility for a Percy Jackson fanfiction centered around the Primordial Son of Chaos could be a story where Percy discovers a hidden prophecy related to this powerful being. Maybe he has to team up with some unlikely allies, like a group of minor gods who are also interested in the balance that the Primordial Son of Chaos might disrupt or uphold. This could lead to a series of adventures across different realms, including Tartarus, where they search for clues about the true nature of the Primordial Son of Chaos.
I'm not sure specifically as there could be many different interpretations of such a fanfic. It might be about Percy being portrayed as a true child of Chaos in a unique story setting, perhaps with new powers, relationships, and adventures.
Percy's friends from Camp Half - Blood could also be important. They might react in different ways to Percy's new status as the Son of Chaos. Grover, for instance, could be torn between his loyalty to Percy and his fear of the new and unknown powers Percy wields. Nico might also have a significant role, perhaps using his own dark powers to help Percy understand and control his Chaos - related abilities. These characters add depth to the story and create a sense of continuity with the original Percy Jackson series.
There are some fanfictions that focus on the relationship between Percy and Zoe in the context of Percy being the 'Son of Chaos'. In these, they often have to deal with the mistrust from other demigods at first. But as the story progresses, they prove their worth and their relationship deepens, like in a story where they go on a quest to retrieve a powerful artifact that can only be controlled by a 'Son of Chaos' and his trusted ally, which is Zoe in this case.
The plot could center around Percy's transformation into the 'Son of Chaos'. He might have to face challenges that test his loyalty to his old friends at Camp Half - Blood while also adapting to his new role. He may also encounter new characters who are either allies or enemies in this new phase of his life. It might also involve a power struggle within the chaotic realm where he has to prove himself worthy.
Well, perhaps the plot involves Percy being hunted by various forces. The Olympians see him as a threat because of his Chaos lineage, and the minions of Chaos might think he's too much of an Olympian. He then has to form an unlikely alliance with some demigods and minor gods who believe in his unique potential. Along the way, he uncovers secrets about the origin of the gods and the true nature of the relationship between Hera and Chaos.
One interesting plot could be Percy finding a way to balance the powers of Chaos and Order within himself. He might have to face challenges where the two opposing forces are at war inside him, and he has to learn to control them without being consumed. For example, when he's in a battle, the chaotic side might want to go all - out destruction while the order side wants a more strategic approach.