Nico di Angelo might also be a key character. He has powers over the dead and the underworld, which could be helpful in finding out if Percy is still alive or in some other realm. He could use his powers to communicate with spirits that might have seen Percy's disappearance.
His friends like Annabeth would surely be main characters. She is smart and resourceful, so she would be leading the search for Percy. Grover could also be a major character. He has a strong sense of loyalty and his connection to nature could be useful in tracking Percy down.
The gods are always a possibility. Zeus, for example, has been distrustful of Percy in the past. If Zeus feels that Percy is getting too powerful or is a threat to his rule, he could engineer a situation where Percy is betrayed. He might use other demigods or even mortals to turn against Percy.
A group of rogue demigods could be the main antagonists. They believe that Percy is too powerful and his presence is causing more problems than solutions in the demigod world. So they make him disappear. But when Percy comes back, he shows them that they were wrong and that they have been mislead by false beliefs.
Luke could also be a prominent character. Since he has a complex relationship with Kronos in the original story, in fanfiction he could play a role in either helping or hindering fem Percy's efforts against Kronos. Nico di Angelo is another possibility. His powers over the dead could be useful in a fight against Kronos, and he might team up with fem Percy for that reason.
There could be a new character, a jailmate of Percy. This character could be either a friend who helps Percy survive in jail or an antagonist who makes his life more difficult. For example, a tough guy who wants to bully Percy at first but later has a change of heart.
Another character could be Annabeth. She might try to stop Percy from taking such extreme actions, or she could be on his side if she believes the hunters are in the wrong. Grover could also be there, trying to play the peacemaker between Percy and the hunters. And then there could be some new, made - up characters in the fanfiction, like a rogue hunter who sides with Percy or an antagonist within the hunters' ranks who pushes Percy to his limits.
In the 'Percy Jackson Disappears' fanfiction, perhaps Percy could be kidnapped by an unknown enemy. Maybe it's a new villain who has a vendetta against the demigods. This would lead to his friends, like Annabeth, going on a desperate search for him, facing many dangerous challenges along the way.
One possible plotline could be that Percy has been kidnapped by some mysterious enemy. Maybe it's a new villain who has a vendetta against him. His friends then start a search mission to find him, facing various challenges along the way.
There could be the typical Dragonborn - associated characters. Maybe characters like Delphine, who often plays a role in guiding the Dragonborn. Since Percy is now the Dragonborn, she might interact with him in different ways compared to the original game.
Aside from Percy, Silena Beauregard from the Aphrodite cabin could be a key character if she's still alive in the fanfiction's timeline. She might be conflicted about the kidnapping since she has friends outside the cabin. And of course, Grover could be involved too. He would sense that Percy is in trouble and try to use his nature - related powers to track him down.
Grover could also be a main character. He might be at the scene when Percy gets drunk and try to use his nature - related powers to sober Percy up. Grover could also provide some comical relief with his reactions to Percy's drunken state, like his horrified expressions or his attempts to herd Percy like he would a wild animal.