I'm not sure specifically who 'harry potter king of fanfic' is. It could be a fanfiction author who is very well - known in the Harry Potter fanfic community for creating really great stories.
Obviously, Harry Potter is one of the main characters. Since it's about him being a king in some way. Hermione Granger and Ron Weasley are likely to be main characters as well, as they are Harry's closest friends and would play important roles in his new 'king' - like journey. There could also be other characters like Dumbledore, either in spirit or through memories, guiding Harry in his new role.
Obviously, Harry Potter would be one of the main characters as it's about him being the rightful king. Hermione and Ron might also be important as they usually support Harry in his adventures and would likely be by his side in this new role as well.
In the 'Harry Potter Serpent King Fanfic', Harry Potter is bound to be a central figure. He might be the one who has to face the challenges posed by the Serpent King. Besides, Hermione and Ron could also be important characters. They often stand by Harry in the original series and might do the same in this fanfic. And the Serpent King himself is a main character. He could be a complex figure with his own motives and backstory that the fanfic will gradually reveal.
Well, Harry Potter is bound to be a central figure in this fanfic. The wolf king is another main character. It's possible that other characters from the original series could play important roles too. For instance, Dumbledore might offer some wisdom or guidance regarding the wolf king. Or perhaps some of the darker characters like Voldemort's followers could be interested in the power of the wolf king and try to get in Harry Potter's way as he deals with this new entity. Neville could also be a character in this fanfic, showing his growth and courage as he helps Harry Potter face the challenges related to the wolf king.
Most likely Harry Potter would be one of the main characters. Since it's a crossover with the Potter universe.
Most likely Harry Potter himself as he is in the title. And probably his friends like Hermione and Ron might also be important characters, still supporting him in this new 'king of magic' scenario.
Obviously, Harry Potter himself. Hermione and Ron would most likely be there too, as his closest friends. Dumbledore might still play a role, perhaps as an advisor to Harry in his new position. And there could be new characters, like wizards and witches from other parts of the world who come to see the new king.
Well, without reading the specific fanfiction, it's hard to tell exactly who the king is. It could be an original character created by the author, or perhaps it's a character from another fictional universe that the author has incorporated into the Harry Potter world for this unique plotline.
One idea could be a fanfic where Harry Potter discovers a hidden portal in Hogwarts that leads him to the time of King Arthur. He could use his magic skills to assist Arthur in battles, perhaps using spells to defeat the enemies that Arthur's knights struggle with. For example, Harry could use the Stunning Spell to incapacitate a large group of invaders.
It could be about Harry Potter being seen as the rightful king in a fan - created story. Maybe it involves a scenario where he has a claim to some sort of throne within the wizarding world, perhaps in an alternate version of the events we know from the original books.