The other demigods at Camp Half - Blood would also be in chaos. Percy was like a leader to many of them. His death could lead to a lack of confidence among the younger demigods. Some might even start to question the protection of the gods. Zoe's survival could also lead to her taking on a more prominent role in guiding and protecting the demigods, which is a big change from her previous situation.
Maybe in the fanfic, Percy's death could be a sacrifice to save Zoe. This would then lead Zoe to live her life in a way that honors Percy's sacrifice. She could become a protector of the things Percy held dear, like a certain place or group of people. And as she does this, she has flashbacks of their time together, which are bittersweet memories that keep her going.
The characters would be devastated. Grover, Percy's best friend, would be heartbroken. He might lose his ability to find Pan because of the emotional turmoil. His search for Pan was always connected to his friendship with Percy, and without Percy, he could be lost.
One possible plot development could be that when Percy dies, his friends are devastated. They might embark on a quest to find a way to bring him back. In the process, they discover some long - hidden secrets about the gods. Another development could be that Percy's rebirth gives him new powers, which he then uses to fight a greater threat that was emerging even before his death.
One possible plot development could be that Peter is left with a huge sense of guilt. He might struggle with survivor's guilt, constantly thinking that it should have been him. He could then become overly reckless in his superhero activities, trying to prove that he was worthy of being saved. Another aspect could be how the other Avengers deal with Tony's death. They may turn to Peter as a symbol of hope, since Tony sacrificed himself for Peter. This added pressure on Peter could lead to him either rising to the occasion or crumbling under it.
One possible plot development could be that his friends are left to pick up the pieces. They might struggle with grief and guilt, thinking they could have saved him. Another could be that Voldemort finally takes over completely without Harry to oppose him, leading to a dark reign over the wizarding world.
One possible plot development could be that Sasuke is in a life - threatening situation, perhaps against an extremely powerful enemy. Naruto sacrifices himself to give Sasuke a chance to escape or defeat the foe. This would likely lead to Sasuke being filled with guilt and regret, and might change his whole outlook on life.
Perhaps Percy's torture makes Annabeth realize the depth of her feelings for him. Before, she might have been unsure or in denial, but seeing him in such pain makes her confront her emotions. This could lead to a more intense relationship between them once Percy is saved. For example, she could be more open and affectionate towards him.
One possible plot development is that the gods gather to hold a trial for the abuser. They would bring in witnesses, and Percy would have to testify about what happened to him. This would be a very emotional and intense scene.
Perhaps the story could take a really dark turn. With Bella dead, the Volturi might see this as an opportunity to assert more control over the Cullens. They could come to Forks under the pretense of investigating Bella's death but really be there to intimidate the Cullens into following their strict vampire laws more closely. Meanwhile, Jacob could struggle with his own identity and his role in Bella's death. He might feel like he failed to protect her, and this could lead to him making some rash decisions in his werewolf form, endangering not only himself but also his pack.
One possible plot development could be that Voldemort fully regains his power without Harry as an obstacle. The wizarding world would be plunged into complete darkness. His friends, like Hermione and Ron, might go into a deep state of despair and then form a resistance group. They would try to find other ways to defeat Voldemort, perhaps by seeking out more powerful magical artifacts or uniting with some previously neutral magical creatures.