One possible plot could be that the murderer is a jealous rival. Maybe this rival has always been envious of Percy's popularity or special abilities, and finally decides to get rid of him. Another plot could involve a mystery where Percy is murdered and his friends have to piece together the clues to find out who did it. It could be that the real killer is someone they least expected, like a seemingly friendly acquaintance who has a hidden agenda.
In a 'percy is murdered' fanfic, the plot might revolve around a wrong - place - wrong - time scenario. Percy could be in the wrong place when a powerful and evil force is on a rampage. This force simply kills Percy without really having a personal vendetta against him. However, his death becomes a catalyst for the rest of the characters to come together and try to stop this greater evil.
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.
One possible plot could be Percy having to deal with new powers. He might struggle to control them at first, like accidentally causing thunderstorms when he's angry. Another plot could involve other characters' reactions. His friends might be in awe or a bit scared. For example, Annabeth could be worried about how this change will affect their relationship. Also, Percy could face new enemies who are jealous of his new god - like status or want to use his powers for their own evil plans.
Perhaps the fanfic could start with Lemon discovering a prophecy that involves Percy and Khione. They then have to come together to figure out what the prophecy means. Along the way, they face various challenges. Khione's powers might be waning, and Percy has to use his powers to protect her while Lemon tries to find a way to restore her powers. This could lead to a deep bond forming between the three characters as they rely on each other.
It could be that an anonymous assassin is the suspect. This assassin could have been hired by someone who wants Percy out of the way but doesn't want to get their hands dirty. Or perhaps a possessed character could be the suspect. They have no control over their actions when they kill Percy as they are being controlled by a malevolent spirit.
One possible plot could be that Annabeth is under some kind of mind control. Maybe a powerful enemy has taken over her mind, forcing her to turn against Percy. Another could be a misunderstanding. For example, she might think Percy has betrayed her or their friends in some way, leading to a tragic confrontation.
One possible plot could be Percy being framed for a crime he didn't commit by the Olympians. Maybe they needed a scapegoat for something that went wrong in the mortal world that they didn't want to take the blame for. Another plot might involve Percy discovering a dark secret about the Olympians that they don't want him to reveal, so they turn on him to keep him silent. It could also be that a new powerful enemy has influenced the Olympians against Percy, perhaps by spreading false rumors or using some form of mind control on them.
Maybe there's a prophecy at camp that some misinterpret to mean Percy will bring destruction. So, the campers, out of fear for their safety, betray Percy. They could lock him up or try to send him away, even though Percy has always been loyal to the camp. He then has to find a way to either clear his name or find a new place where he belongs.
One possible plot could be that Percy's friends immediately start a search and rescue mission. They follow the limited clues left behind at the kidnapping site. Another could be Percy manages to endure the torture and uses his wits to outsmart his captors from within.
One possible plot could be Percy getting drunk and accidentally revealing his true feelings to a friend or love interest. For example, he might finally admit his long - hidden admiration for Annabeth while in a drunken state.
One possible plot could be Percy trying to ask someone out on a date but his shyness getting in the way. He might stutter, blush, and find it difficult to form the right words.