In many 'Stiles is not human fanfiction', Malia could play a significant role. Given her own complex backstory and her were - coyote nature, she might be able to relate to Stiles in some ways if he's not human. She could either help him adapt to his new state or be in conflict with him. Kira could also be involved. Her kitsune powers and her kind nature might lead her to try and understand Stiles. And the Sheriff, Stiles' father, is bound to be in the story. His relationship with Stiles would be put to the test as he discovers his son is not what he thought he was, and he'd have to deal with his own emotions and the potential danger that Stiles' non - human nature could bring.
Well, aside from Stiles, Scott is bound to be a central character. Their friendship is so strong that Scott would immediately start looking for ways to rescue Stiles. Derek Hale is another likely character. Given his past with the alpha pack and his relationship with Scott and Stiles, he would have a role to play. Then there's Allison. Her family's history with the supernatural means she has skills and knowledge that could be useful in rescuing Stiles. She could be involved in the search and rescue operation, using her archery skills and knowledge of the supernatural world to help out.
Scott is often paired with Stiles. Their friendship is a central part of the original series, and in fanfiction, it can be explored in new ways when Stiles isn't human. Scott might have to deal with the changes in Stiles and still maintain their bond.
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.
There could be a tough drill sergeant who acts as a mentor and a source of conflict for Stiles. This character would be strict but fair, and would push Stiles to his limits.
Obviously, Stiles is the main character. Then there are usually her friends from the pack, like Scott, Derek, and Lydia. Scott might be the supportive friend who encourages the makeover. Derek could be the initially skeptical one but then is surprised by the results. And Lydia might be the one who actually helps with the fashion and style part of the makeover.
Stiles is a must - have main character. Then, depending on the direction of the fanfiction, characters like Simon Lewis could be important. Since Simon is a vampire in the Shadowhunter universe, his interactions with Stiles, who is new to this world, could be really interesting. Also, characters like Luke Garroway, the werewolf, might play a role, especially if the story involves the relationships between different Downworlder groups and Stiles' place in all of that.
Stiles' father could be a major character. He would be worried sick about his son and use all his resources to try and find him. Maybe he teams up with some of Stiles' friends like Scott or Lydia.
The main characters are Stiles and the Cullens. Stiles is known for his ability to adapt in strange situations. When he meets the Cullens, their interactions will be centered around how they deal with each other's differences. The Cullens' vampiric abilities and Stiles' human (or whatever he is in his original context) nature will play a big part in their relationships in the fanfiction.
Well, obviously Stiles is one of the main characters. He's the one being hurt by the pack. The members of the pack would also be main characters, though we don't know exactly which ones without more context. It could be Scott, as he's often a central figure in the pack. There might also be other characters like Derek who could be involved in either causing the hurt or helping Stiles deal with it.
Stiles is the central figure in this fanfiction. Since he's a born vampire, he has his own set of characteristics and story arcs. His father could also be a significant character. In many fanfictions, the relationship between Stiles and his father is explored, especially when his father starts to suspect that something is different about his son. Additionally, if there are any vampire mentors or antagonists in the story, they would be main characters as well. They would either guide Stiles in his vampire journey or try to stop him from achieving his goals.