Well, perhaps in this fanfiction, Percy and Piper join Chaos because they're seeking a way to save the world from a greater threat that the Olympians can't handle. Chaos sees their potential and recruits them. Their journey might involve learning ancient and forbidden magics within Chaos. They could also meet other demigods or creatures who have been part of Chaos for a long time and have to prove themselves worthy to these new allies.
It could be an ancient and powerful being from the chaos realm who sees Percy and Piper as intruders and a threat to its own power. This being might have been ruling over a certain part of Chaos for eons and doesn't want the demigods to disrupt the status quo.
One common theme is the disruption of the normal order. For example, in many stories, the gods' rules or the Camp Half - Blood's usual way of life is thrown into chaos, and Percy and Piper have to adapt. Another theme is the growth of their characters. Through facing chaos, they learn more about themselves and become stronger.
One key element is the characters of Percy and Piper. Their unique personalities and abilities drive the story. For example, Percy's water - related powers and Piper's charm - speak can create interesting situations in a chaotic setting.
Well, in many 'Percy join Chaos' fanfictions, a key plot point is Percy's relationships. How does he interact with the beings in Chaos? Does he make new friends or enemies? Also, his journey to understand the purpose Chaos has for him. Is he there to save it, change it, or is he just a pawn in a bigger game? These questions often drive the plot forward.
I'm not sure about a specific 'Percy join Chaos' fanfiction off the top of my head. However, when looking for it, consider checking fan communities. They often have discussions and recommendations about such unique crossovers. Some might even share links to their favorite stories.
It could be the agents of Order who see Percy and Thalia joining Chaos as a threat to the balance they strive to maintain. They might send their best warriors to stop Percy and Thalia from carrying out Chaos' plans.
One possible plot could be that Percy and Thalia are tired of the constant battles and politics in their current world. Chaos offers them a new beginning. They join Chaos' forces and are trained in unique ways. Percy might use his water - controlling abilities in new and unexpected ways under Chaos' guidance. Thalia could also enhance her skills with lightning. Together, they go on missions to restore balance in different realms that are in chaos (in a non - traditional sense).
The plot might involve Percy and Jason having to adapt to the new and chaotic rules of the Chaos realm. They could discover new powers within themselves as they are exposed to the wild and unpredictable energy there. They might also meet old enemies who have also found their way into this strange new world, leading to some epic battles and unexpected alliances.