In a 'Percy Jackson kidnapped by Luke' fanfiction, perhaps Luke kidnaps Percy because he believes Percy is the key to unlocking some ancient and powerful magic. Luke could be under the influence of some dark force. Percy would then have to figure out Luke's motives while also trying to break free. He might use his water powers in creative ways to attempt an escape, like creating a distraction with a flood.
Well, one possible plot could be that Luke kidnaps Percy to use him as a bargaining chip. Maybe he wants to trade Percy to the Titans for more power or a higher position. Luke might keep Percy in a secret location, like an old, abandoned temple. Percy, of course, would try to escape and find a way to warn his friends at Camp Half - Blood.
Chiron, the centaur mentor at Camp Half - Blood, might get involved in the rescue. He has a vast knowledge of the demigod world and could use his wisdom and connections to track down Luke and free Percy. Also, some of the other demigods at the camp who look up to Percy might volunteer to help, like Clarisse. She may not like Percy much, but she wouldn't want a fellow demigod to be in the hands of Luke.
One possible plot could be that Percy is being controlled by some dark force. Maybe a new evil god or an ancient curse. This force makes him kidnap Reyna because she has some important knowledge or power that the dark side wants. For example, she might know the location of a powerful weapon that could tip the balance in a coming war between the gods and the titans' remnants. Percy, against his will, takes Reyna to a secret location. Reyna, being a strong and resourceful character, tries to figure out a way to break Percy out of the control while also dealing with the situation at hand.
One possible plot could be that they discover their brotherhood early on. They then team up to face the various challenges in their world. Maybe they use their combined powers, like Percy's water - related abilities and Luke's combat skills, to fight against a common enemy, such as a powerful monster that threatens their home.
Luke in Percy Jackson fanfiction can play various roles. He could be a reformed villain, seeking to make amends for his past actions. This gives a new arc to his character that wasn't fully explored in the original books.
If Luke were good, it could completely change the dynamics of the story. Maybe he'd become a powerful ally instead of an antagonist.
It could be a vengeful minor god. Maybe a god who feels that Percy or the demigods in general have disrespected the gods too much. This god might think that by kidnapping Percy, they can teach the demigods a lesson. Another option is a powerful monster that has a grudge against Percy specifically, like a particularly smart and devious Cyclops who has been plotting revenge.
If Percy Jackson was kidnapped by SHIELD, it would be a chaotic situation. SHIELD is used to dealing with superheroes and advanced technology, but Percy comes from a whole different world of Greek mythology. His loyalty lies with Camp Half - Blood and his friends there. He would be desperate to escape and get back to them. And his demigod abilities would make it really hard for SHIELD to keep him locked up. He could use his sword, Riptide, to break out of any confinement and then use his water - based powers to create distractions and make his escape.
One idea could be that Percy is kidnapped by a group of rogue demigods who want to use his powers for their own gain. They might try to force him to lead them to hidden treasures or secrets in the demigod world. Another plot could involve Percy being kidnapped by a new, unknown enemy from an ancient myth that has been awakened and sees Percy as a key to its revival. Or perhaps he's kidnapped by a powerful sorcerer who wants to steal his connection to Poseidon for dark magic purposes.
In this fanfiction, perhaps there is a misunderstanding between Luke and Percy. Luke might think Percy has betrayed him in some way, like siding with the wrong people in the context of their fictional world, and thus resorts to violence by beating him up.
A great plot could involve a prophecy that centers around their brotherhood. Percy and Luke are initially on opposite sides due to Luke's association with the Titans. But when they find out they are brothers, it throws everything into chaos. They have to navigate their relationship while also trying to figure out how to fulfill or avoid the prophecy. There are a lot of emotional moments as they struggle with loyalty to their respective camps and to each other as family.