Stiles usually reacts with a mix of fear and defiance. He's afraid because he's in a dangerous situation, but his strong - willed nature makes him defiant. For example, in many fanfictions, he'll shout at Peter, trying to show that he won't be easily broken.
There's a fanfic called 'Peter's Kidnapped Prize'. It starts with a very intense kidnapping scene. As the story progresses, it shows how Stiles' friends are trying to find him, and at the same time, Stiles is trying to survive in Peter's clutches. 'Stolen by Peter' is another one. It's unique in the sense that it shows a different side of Peter, not just as a villain but as a complex character with his own reasons for kidnapping Stiles. 'The Kidnapping of Stiles' also stands out as it weaves in some elements of mystery about why Peter chose Stiles in particular.
There could be other members of Peter's pack such as Derek. Derek often plays an important role in stories related to packs. He might be initially skeptical of Stiles being part of the pack.
He could use his intelligence to manipulate Kate. Maybe he convinces her that he is more useful to her if he is free, and she lets her guard down long enough for him to make a run for it. Also, he could have some hidden skills or knowledge that he uses to break free. Say he knows a spell or a code that unlocks his restraints or the door to his prison.
It could be a rogue werewolf. Maybe this werewolf has a grudge against Stiles' pack and thinks that by kidnapping Stiles, he can get some sort of revenge or leverage.
There's a fanfiction where Stiles is kidnapped by a supernatural being and tortured in a hidden lair. It focuses on his attempts to escape and the friendships that help him through it. The author does an excellent job of building tension throughout the story.
On the other hand, Stiles is also known for his quick thinking. He might start to try and bargain with Peter. He could offer to help Peter in some way if Peter lets him go. For example, if there's a problem in the supernatural community that Peter is facing, Stiles could say he'll use his human ingenuity to solve it. Also, Stiles could be angry. He might start shouting at Peter, calling him out on his actions, and trying to make Peter see how wrong this is.
At first, it might be a tentative alliance. Stiles could be initially drawn to Peter for his knowledge. Peter, seeing Stiles' potential, starts to include him more in his plans. As time goes on, they might develop a mutual understanding. Stiles begins to trust Peter more and more, and Peter starts to value Stiles not just for his help but also as a friend or something more.
It could be that Stiles is in some kind of danger, perhaps from another supernatural being. And he goes to Peter because Peter has certain powers or knowledge that could protect him. For example, Peter might know how to defeat a particular enemy or how to get out of a tricky situation involving magic or some other supernatural element.
One common theme is the exploration of their complex relationship. Since they have different personalities and backgrounds in the show, fanfiction often dives into how they interact and influence each other. Another theme is the supernatural elements. Given the nature of the show, stories might involve them facing supernatural threats together or having unique supernatural abilities related to their bond.