Some of the gods might also be important characters. Poseidon, Percy's father, could have an interesting reaction to Percy's new relationship. Hades, as the god of the underworld where Styx is located, might also be involved, either as an ally or an obstacle depending on the direction of the fanfiction.
Well, clearly Percy Jackson is one of the main characters. He's a well - known demigod in the Percy Jackson universe. And of course, Lady Styx is another main character in this fanfiction. She has her own powers and influence in the Underworld.
In this fanfiction, Percy Jackson is the central figure as he controls the Styx. But other important characters could be Grover, his satyr friend. Grover has always been there for Percy and could provide support or comical relief. Also, Nico di Angelo could play a significant role. Given his connection to the underworld, he might have some insights or even a conflict with Percy regarding the control of the Styx.
Obviously Percy Jackson himself is a main character as it's about his dip in the Styx. His girlfriend Annabeth Chase would also likely be involved. She's always by his side in tough situations and would be there either to support him before the dip or to help him deal with any after - effects.
Since the title mentions Percy, he's most likely one of the main characters. But without reading it, it's hard to say who else might be important. There could be characters from the original series that Percy is from, if this is a fanfiction based on an existing franchise. Maybe his friends or mentors could be involved too.
Another interesting plot could be Percy's internal struggle. He's used to being Poseidon's son, and now this new connection to Styx throws his identity into a bit of chaos. He has to figure out how to balance his old self with this new aspect of his being, all while facing various quests and threats in the Percy Jackson universe.
It could be an old enemy of Percy who has somehow gained power over the Styx. Maybe a resurrected villain from Percy's past who now wants to use the power of the Styx to take revenge on Percy and the gods. For example, Kronos' remnants could have found a way to manipulate the Styx's energy for their own evil purposes.
The Titans could still be a major threat. Even if Lady Styx is involved, the Titans might see an opportunity to use the chaos she causes to their advantage. For example, Kronos could try to ally with Lady Styx to regain his power and overthrow the Olympians once again.
In a fanfiction of Percy Jackson dipping in the Styx in Tartarus, it might explore the idea of him getting new powers or a stronger connection to his godly side. For example, his water - controlling abilities could become more refined and he could have a better understanding of the Underworld's waters. Also, he could encounter some long - forgotten spirits or creatures that guard the Styx in Tartarus.
Well, sometimes in fanfiction, his brother might be a mortal who discovers his demigod heritage later. This could add an interesting twist to the story as he has to adapt to the world of gods and monsters. Or it could be a long - lost half - brother from a different camp, like a son of Poseidon from another part of the world who was hidden away for some reason.
Well, in this fanfiction, Percy controlling the Styx could lead to some really interesting plot developments. Since the Styx has such a significant role in Greek mythology, it could attract all kinds of mythical creatures and gods. Percy could find himself in the middle of a power struggle as different factions either try to use him or stop him. He might also use the Styx to travel to different realms or access hidden knowledge. And perhaps he would have to face the consequences of messing with such a powerful and sacred entity, like facing the wrath of Hades or other underworld deities.