In a fanfiction like this, Percy might die due to a curse placed on him. His death could be a shock to everyone, especially Annabeth. But as he dies, his soul could travel to a mysterious realm where he has to pass certain trials. After succeeding, he gets reborn with a deeper understanding of his powers and his destiny. His rebirth could also bring about a change in the relationship between demigods and gods, as they now see him as a symbol of hope and resurrection.
Well, perhaps he could die sacrificing himself to save his friends from some ultimate evil. Then, his rebirth could be linked to a powerful ancient magic. Maybe a forgotten god decides to bring him back for some grand purpose, like to stop a new threat emerging in the world of the gods.
One possible plot could be that Percy dies in a battle against a new and extremely powerful monster. His death could cause chaos among his friends and the demigod community. But then, his spirit is somehow preserved by a magical force, like the power of the ocean itself. And he gets reborn with enhanced powers, ready to face the new challenges that await him.
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.
It could be a new Titan that has been awakened from an ancient slumber. This Titan might be angry at the gods for imprisoning them long ago and wants revenge. Percy's death could be part of the Titan's initial plan to strike fear into the hearts of the gods and demigods, but Percy's rebirth becomes a major obstacle for the Titan.
Well, one possibility could be that Percy discovers a new aspect of the mythological world. Maybe in this fanfic, his death is a sacrifice to save his friends. Once in Valhalla, he could meet new heroes from different mythologies and form alliances or rivalries. He might also try to find a way back to life or to his friends in the world he left behind.
One possible plot development could be exploring how Percy and his friends deal with this unexpected situation. Maybe they would have to face the reactions of the demigod community. It could also lead to Percy having to grow up very quickly and take on more responsibilities.
Maybe he faced an extremely powerful enemy that he couldn't overcome. It could be a new and terrifying monster created by the Titans or some other dark force.
In this fanfiction, it could be that Artemis is in a situation where she is about to be killed or lose her powers forever. Percy, being the selfless hero he is, takes on a deadly task to prevent that from happening. Maybe it involves facing an ancient and malevolent god who has a vendetta against Artemis, and Percy uses his unique abilities and the element of surprise to try and stop this god, but at the cost of his own life.
A possible plot in such a fanfic could be Percy trying to bring Sally back from the dead. He could go on a dangerous and forbidden quest, defying the gods and the natural order. This would put him at odds with many, but his love for his mother is so strong. He might encounter dark magic or make deals with shadowy figures in his desperation, all while his friends are worried about him losing himself completely in this quest.
It might also be related to some sort of enemy or threat that specifically targets Percy and his relationship with Annabeth. The enemy could be so powerful that Percy realizes the only way to stop it from harming Annabeth is to sacrifice himself, like if the enemy feeds on his life force or his connection to Annabeth, and he chooses to end it by sacrificing his own life.
It could be a new, powerful Titan that was previously unknown. This Titan might have a vendetta against Percy specifically, seeing him as a major threat to their plans. Maybe they manage to kill Percy, but his rebirth sets in motion a series of events that will lead to their ultimate downfall.
One possible plot twist could be that Triton is not actually there to help Percy but is being controlled by an enemy to spy on him. So, Percy might think he has a new ally but in fact, he is being set up.