Dumbledore could also be a major character. He would be faced with the dilemma of how to deal with Harry's transformation. Does he try to find a way to reverse it? Or does he accept it and help Harry use his new powers for good? His wisdom and guidance would be crucial in Harry's journey as a born vampire, and his decisions could have far - reaching consequences for the wizarding world as a whole.
Obviously, Harry Potter himself would be the central character as he is the one undergoing the transformation into a born vampire. His friends like Hermione and Ron would also be important characters. They would likely play a role in either helping Harry adjust or being conflicted about his new state.
The main characters Damon and Bella will interact with each other on multiple levels. Damon will probably teach Bella about the vampire way of life. There could be other vampires from different clans that cross their path. These vampires might be curious about Bella or have their own agendas. Additionally, if the fanfiction has a touch of the supernatural world at large, angels or demons (if they exist in that universe) could also interact with them, adding a whole new layer of complexity to the story.
Hermione and Ron might still be in the story, but their interactions with Harry would be completely changed. Since Harry is a Malfoy, they might initially be enemies or at least very suspicious of him. However, as the story progresses, they could see the good in him that is still there despite his Malfoy background. And Dumbledore would also be an important character, as he might try to guide Harry away from the darker Malfoy influences.
Harry is the central figure in 'harry turns into a snake fanfic'. In addition to his closest friends, there could be some new characters introduced. For instance, an old wizard who specializes in transfiguration gone wrong. This wizard could be a hermit living on the outskirts of the wizarding world. He might have the key to understanding Harry's transformation and reversing it. And we can't forget the snakes themselves. There could be a particularly intelligent snake that befriends Harry in his new form and helps him in his journey.
Obviously, Deku himself would be a main character even though he's turned into a baby. His friends like Uraraka, Iida, and Bakugo would also be main characters as they would be involved in taking care of him and trying to solve the problem.
Obviously, Itachi as a baby would be a main character. Sasuke would also be a key character as Itachi's brother. Their relationship would be very different now that Itachi is a baby. Naruto could also be involved, perhaps being curious about this strange transformation and wanting to help out in some way.
There could also be some sort of vampire elders or leaders that are part of the story. Since Edward is a born vampire, they might be interested in him or have some sort of plan regarding him. Their presence would add to the complexity of the story and the relationships within 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.
Well, Bella is obviously one of the main characters. Since it's about her being born a vampire, she will be central to the story. There might also be other vampires that she interacts with, like the Cullens if it follows the Twilight universe to some extent.
It could be a powerful vampire clan that doesn't want Harry, a new vampire, to disrupt their ways. They might try to either kill him or force him to join their ranks against his will. They could see him as an outsider who doesn't belong in the vampire world and a potential danger to their secrecy.
One possible plotline could be Harry struggling to control his new vampire instincts while still trying to protect his friends at Hogwarts. He might have to deal with the thirst for blood while attending classes and facing off against the Dark Arts. Another could be that he discovers a whole new vampire community within the wizarding world that has its own rules and power structures.