Percy might endure it through his own stubborn will. He's a demigod used to facing tough situations. In this fanfiction, he could be using his past experiences of fighting monsters and surviving hardships. He might tell himself that he's been through worse and this is just another trial he has to pass. So he grits his teeth and bears it as best he can, even when the torture in Tartarus is beyond what he's ever faced before.
Maybe it's part of a plot to have Percy gain some sort of power or knowledge. In many fictional stories, a character has to go through great pain and suffering before emerging stronger or wiser. The torture in Tartarus could be a way to set up this transformation for Percy.
Another scenario could be that Percy is forced to endure extreme environmental conditions in Tartarus. The place is known for its intense heat, toxic fumes, and jagged terrain. He might be made to traverse through burning lava fields or climb sheer cliffs while being constantly weakened by the poisonous air, all of which would be a form of torture.
In some fanfictions, Percy's torture in Tartarus could be part of a grander scheme. For example, an enemy on the surface world has made a deal with the forces of Tartarus to weaken Percy. As he endures the torture, he gradually uncovers the conspiracy and tries to find a way to not only escape but also stop those who sent him there. His friends, unaware of his situation at first, start to suspect something is wrong and embark on a quest to find out what happened to him and rescue him.
He might use his powers in creative ways to lessen the impact of the torture. For instance, if the torture involves some form of mental attack, he could try to use his connection to water to calm his mind. Also, his demigod abilities, like his superhuman strength and agility, could help him physically resist some of the more brutal forms of torture to a certain extent. And he may also draw strength from the memories of his past victories and the people he has saved.
It could be the traditional villains from the original story. Maybe some of the old enemies of Percy who have a vendetta against him. For example, the Titans or some rogue demigods who oppose him for power or personal reasons.
One common theme could be the exploration of Percy's inner strength. Through the torture, the story might show how he endures and overcomes. Another theme could be the reaction of his friends. They might be desperate to save him, highlighting the bonds of friendship. Also, it could explore the motives of the torturers, whether it's for revenge or some other dark purpose.
In the fanfiction, if Percy gets banished to Tartarus, he could potentially meet some old enemies who have been banished there too. Maybe he'd have to team up with some unlikely allies to find a way out. It would be a struggle for him, as Tartarus is a place where hope is almost non - existent. He'd also have to deal with the harsh environment, like the rivers of fire and the jagged rocks.
One interesting plot could be Percy's struggle to survive in Tartarus alone. He might have to face the various monsters there without his usual allies. Another plot could involve him finding a way to escape Tartarus using his wits and the powers he has. Maybe he discovers some secrets about Tartarus that no one else knows.
A third plotline could be about Percy's mental and emotional state during his banishment. He could be dealing with feelings of betrayal, as he was banished. He might question his identity and purpose, and throughout the fanfiction, he gradually overcomes these doubts and insecurities, emerging stronger in character even if he's still trapped in Tartarus.