There could be an entirely new character as the 'no life king' who is the main focus. Alongside this character, there might be some minor characters from the original Harry Potter series who interact with them. For instance, perhaps a Hogwarts professor who tries to guide this 'no life king' character back to the right path if they are causing trouble in the school or the wizarding community. Or it could be a fellow student who befriends the 'no life king' and helps them see the world in a different way.
Since I haven't read this particular fanfiction, it's hard to say for sure. But it could feature Harry Potter himself, maybe he encounters this 'no life king' character and has to deal with whatever chaos or mystery they bring. It might also include his friends like Ron and Hermione who could be involved in trying to understand or stop the 'no life king' if they pose a threat.
Obviously, Harry Potter is a main character. In addition, it's possible that Voldemort could be involved in some way. Maybe Voldemort is trying to take over the role of 'King of the Dead' or is causing chaos in the realm of the dead that Harry has to stop. Neville could also be a significant character, perhaps he has some knowledge or power that is useful to Harry in his new adventure as the 'King of the Dead'.
Obviously, Harry Potter is the central character. He is the one with the title 'King of Serpents' in this fanfiction concept.
Harry Potter is the main character. However, depending on the direction of the fanfiction, it could include other important characters. Neville could be one of them, if the story is about how Hogwarts students support Harry in his new role. There could also be antagonists from the abyss itself, like a powerful dark entity that wants to overthrow Harry. And what about Luna? She might have some unique insights or abilities that are useful in the context of the abyss, so she could also be part of the story.
Well, surely Harry Potter is one of the main characters since it's in the title. There might also be his friends like Hermione and Ron, who could be involved in his journey as the 'king of shadows'. Maybe they help him or try to stop him if he goes down a dark path. Other possible main characters could be new villains or allies that are specific to this fanfiction's plot.
Ron and Hermione would probably also be main characters. They have always been Harry's closest friends, so they would most likely be involved in his journey to becoming this 'king of kings'. They could offer advice, support, and their own unique magical skills to help Harry.
Obviously, Harry Potter would be one of the main characters. And the Dragon King, of course. There might also be Harry's friends like Hermione and Ron who could get involved in the story related to the Dragon King.
Obviously, the King of Snakes would be a main character. This could be an original character created for the fanfiction. Harry Potter himself might also be a main character, as the story is set in the Harry Potter universe. His interactions with the King of Snakes could be a major part of the plot.
Harry Potter would surely be one of the main characters as it's in his name. And his friends like Hermione and Ron might also be important. Since it's about the king of the undead, there could be some new characters introduced who are undead themselves, like a vampire wizard or a zombie witch that either help or oppose Harry in his new role.
There might also be some new characters introduced. For example, some powerful wizard or witch from an old and noble family who either supports or opposes Harry's rule. And perhaps some Muggle - born wizards who look up to Harry as a symbol of change and hope in the wizarding world that is now under his leadership as King of the Britons.
In some fanfictions, Voldemort could also be a key character in relation to the snake king. Since Voldemort had a connection with snakes, he might either be in conflict with the snake king for power or try to control it. Additionally, there could be original characters created for the fanfiction. For example, a young wizard who has a special gift for understanding snakes and becomes the mediator between the snake king and the human wizards. This character could bring a fresh perspective to the story and help in building a relationship between the two very different worlds of humans and the snake king.