Percy's change can change the power dynamics in the story. If he's not as confident or as strong - willed as before, it could affect how the group makes decisions. In fanfiction, this can be used to explore different leadership styles or group dynamics. Maybe someone else has to step up and take on a leadership role that Percy used to fill, and this new situation can create all sorts of interesting plot twists.
It can also lead to new character development arcs for other characters. If Percy is different, those around him have to adapt. Annabeth might have to learn how to deal with this new Percy, which could be a whole new plotline in the fanfiction. Maybe she tries to bring back the old Percy, or she has to fall in love with this new version of him all over again.
Well, in most fanfictions where Percy trains in Tartarus, it often involves him facing extreme challenges. He might be learning to control new powers or just surviving the harsh environment. For example, he could be training to fight stronger monsters that lurk in Tartarus.
Well, they would probably communicate better. In Tartarus, they had to rely on clear communication to survive. So, back in the normal world, this would carry over. They'd be more open about their feelings, fears, and plans, which would strengthen their relationship in a more emotional way.
Well, one possibility could be Percy facing his inner demons. In Tartarus alone, he might have to deal with the memories of his past failures and the fear that comes with being in such a desolate place. He could encounter strange and terrifying creatures that test his combat skills and his will to survive.
Well, in many fanfictions, Percy might be on a mission to assassinate some powerful being in Tartarus. Maybe he has to face all kinds of hellish creatures and overcome insane challenges. It could involve him using his water powers in unique ways, like creating weapons out of water to fight the demons of Tartarus.
One possible plot could be Percy and Zoe facing numerous dangerous monsters in Tartarus. They might have to rely on each other's unique abilities. For example, Percy's control over water could help them cross certain deadly rivers while Zoe's hunting skills could be used to fend off the approaching beasts.
One possibility could be Percy's struggle to survive the harsh conditions. He might have to find new ways to use his powers in Tartarus. For example, the strange and dark magic there could either enhance or limit his abilities. He could also form alliances with unexpected creatures. Maybe he teams up with some of the ancient and terrifying monsters that live there, but they have a common enemy, so they work together for a time.
Percy could become more self - reliant. In Tartarus, he can't always count on his friends or his powers in the same way as on the surface. So he'll have to dig deep within himself to find new strengths. He may also become more strategic in his thinking, as one wrong move in Tartarus could mean death.
It makes him more hardened. The harsh conditions force him to become tougher both physically and mentally. He has to constantly be on guard and ready to fight, which sharpens his reflexes and his ability to think quickly in dangerous situations.
His relationship with Annabeth would be severely strained. Annabeth, who has always known Percy as Poseidon's son, would be confused and a bit distrustful. She might think Percy has been lying to her all this time. His friends at Camp Half - Blood would also be divided. Some would be scared of his new powers and his connection to Tartarus, thinking he could be a danger. However, some might be more understanding, especially those who have faced their own identity crises. His relationship with the gods would also change. The gods who were once somewhat friendly or at least neutral towards him might now see him as a threat. Zeus, for example, would be extremely wary of Percy's Tartarus - related abilities.
Well, one possibility is that Percy has to deal with the various monstrous creatures in Tartarus. He might form alliances with some of the less evil ones to maintain order. Maybe he uses his powers over water in unique ways in the dark and chaotic environment of Tartarus.