A vetala elder who has seen many centuries pass could also be a main character. This character could have a wealth of knowledge about the vetala world and play a role in guiding or opposing the 'becoming' aspect in the fanfic.
A young and curious human who stumbles upon the world of vetalas could be a main character. They might start off as an innocent bystander but get drawn deeper into the vetala lore.
Maybe a half - vetala, half - human hybrid who is trying to understand their identity. They would be constantly torn between the two worlds and their struggle could form the core of the story in the fanfic.
One idea could be a character who discovers they have a latent ability to communicate with vetalas and must use this to stop an ancient evil vetala from rising. Another could be a vetala falling in love with a human and the challenges they face in their relationship within the supernatural world.
Obviously, Elena should be the main character. She could be joined by her friends from the original 'vd' story. For example, Stefan and Damon who could either help or hinder her in her journey of 'becoming'.
The main characters in the Cindy123 Supernatural Fanfic could very well be the Winchester brothers. They are iconic in the Supernatural world. But depending on the creativity of the writer, there could be other characters like angels or demons that play significant roles. Maybe there's a human character who has a special connection to the supernatural, like being a seer or having some sort of magic ability that was given to them. It all depends on how Cindy123 has developed the story.
The owner of the supernatural restaurant could be a main character. She is a centuries - old vampire who has seen the world change but has always maintained this one special place. And there could be a detective who is investigating strange disappearances that seem to be related to the restaurant. As he digs deeper, he realizes that the world of the supernatural is far more complex than he thought.
Another possibility is that it could focus on some of the recurring characters from the show but give them a more prominent role. For instance, Castiel could be a main character in this fanfic, and the 'back in black' concept could be related to his journey or a new aspect of his powers.
Since I haven't read it, I can't say for sure. But it could potentially feature the main characters from the Supernatural series like Sam and Dean Winchester, Castiel, or Crowley, if it stays true to the source material in terms of character inclusion.
In many 'becoming a demon naruto fanfic', the main character is often a ninja who has a special connection to the dark or forbidden arts. This connection could be something they inherit, or it could be the result of an experiment gone wrong. There might also be a mentor - like figure who either tries to help the character control their new demon side or is the one who caused the transformation in the first place. And of course, there will be other supporting characters from the Naruto universe, like the Hokage or other ninja comrades, who react to the main character's transformation.
The main character could be a vampire daddy. He has a human daughter that he turned into a vampire at a young age to save her life. Now he has to deal with the consequences of her new existence and teach her how to survive in the vampire world.
Dean and Sam Winchester would be obvious choices as they are the main characters in the Supernatural series. Their experiences and skills would make them well - suited for the new adventures in the fanfiction.
Since I don't know the exact content of the novel, I can't say for sure. But it might have a main character who is on the path to becoming a dragon. There could also be a mentor figure, perhaps an old dragon or a wise wizard who guides the protagonist.