Percy might run into Loki. Loki is known for his trickery. He could either befriend Percy for his own devious plans or try to deceive him. Percy, being used to dealing with tricky situations in his own world, would have to be on his guard against Loki's schemes.
Annabeth is often the one to save Percy. She's smart and resourceful. For example, she might use her knowledge of architecture to find a way out of a collapsing building that Percy is trapped in. Or she could use her strategic thinking to outwit a monster that has Percy at its mercy.
Percy would be completely devastated. He might go into a state of shock at first, unable to believe that Annabeth is really gone. Then he could become filled with rage, vowing to take revenge on whoever or whatever was responsible for her death.
In this type of fanfiction, it's a really interesting concept. One possible scenario could be that Percy's death is a heroic sacrifice. Maybe he gives his life to save the world from an even greater threat than before. And when he becomes a god, he might use his new powers to bring about a new era of peace among the gods and demigods. His transformation could also mean changes in his relationships. For example, his friends might now have to view him in a different light, as a divine being rather than just a fellow demigod.
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.
Annabeth would be devastated. She and Percy have a deep connection. She might go into a state of shock at first, then be filled with a fierce determination to find out who was responsible and make them pay. She would probably also be racked with guilt, thinking she could have done something to prevent it.
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.
Well, if Annabeth dies in a fanfic, it would be a really tragic turn. Percy would be completely devastated. He's been through so much with her, and she's not just his girlfriend but also his partner in all their adventures. Their relationship has been a central part of the Percy Jackson series, so her death would change the whole dynamic. Fans would be heartbroken too, as Annabeth is a very popular character. It could lead to Percy going on a dark path, seeking revenge or just shutting down completely.
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.
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.