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.
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 uses his wits. Percy has always been clever, and in Tartarus, he'd use that to his advantage. He'd find ways to outsmart the monsters, like using the environment against them.
He could rely on his natural demigod abilities. His control over water, for instance, might help him find sources of water in Tartarus that are safe to drink or use for protection. Also, his combat skills, which he has honed over many battles, would be crucial in fending off the various monsters in Tartarus.
He might use his sword skills and his ability to control water. For example, he could create shields out of water to protect himself from attacks. He would also try to find any weaknesses in his enemies. If there are any water sources in Tartarus, he could use them to his advantage, like making geysers to distract or attack his foes.
Grover could also be an ally. His connection to nature might give Percy some unique advantages in Tartarus. Additionally, some of the less hostile creatures in Tartarus, like the friendly Cyclopes, could side with Percy. They might see him as a more just ruler compared to the chaos that usually reigns in Tartarus. Also, Chiron, with his vast knowledge and experience, could offer guidance from afar, which could be considered a form of alliance.
Well, one aspect to consider in this fanfiction could be the character development. Percy Jackson is already a well - established character, but as the heir of Tartarus, he might face new challenges that force him to grow in different ways. Maybe he has to deal with darker powers within himself. Another point could be the world - building. Tartarus is a very dark and dangerous place in the Percy Jackson universe, so how the author expands on that and shows its influence on Percy and the story is important. Also, the relationships with other characters would be interesting. Will his friends still trust him when they find out he has this new 'heir' status? How will his enemies react?
Well, in some fanfictions, Percy might control ice through a new power bestowed upon him by some mysterious god or entity. Maybe he discovers he has the ability during a quest when he's in a really cold and magical place.
A plotline could be Percy having to face his own fears and insecurities while being tortured. Maybe he starts to doubt his abilities and heroism. But as the story progresses, he overcomes these doubts through his willpower. Also, the fanfic could explore how the torture affects his relationship with the gods. He might feel betrayed by them for allowing him to end up in Tartarus and this could lead to a change in his loyalty or attitude towards them.
No, he doesn't in the official series. Fanfictions about his torture exist because fans like to experiment with different plotlines. They might want to see how Percy would react under extreme stress and pain. It gives a chance to show his inner strength or to create a different kind of character development that might not be possible in the main story. It's a way for fans to put their own spin on the character and the world.
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.