In some cases, it might be well - known characters from the original work (if it's a fanfic based on an existing series). For example, if it's a fanfic related to a fantasy book series, it could be the main hero or heroine of that series who has to endure a 'birth by fire' situation to fulfill their destiny.
I don't know for sure as I haven't read it. But it could be characters from the original book series that Book 3 belongs to. Maybe the hero who has to face the challenges related to fire.
I don't know the main characters in 'a taste of fire fanfic' as I haven't read it. But in a typical fanfic, the main characters could be the original characters from the source material that the fanfic is based on.
There could be other characters too, like the Sage of Six Paths. He might play a crucial role in the Juubi's birth in the fanfic. And also, villains from the Naruto universe could be involved, as their actions might have either directly or indirectly led to the birth of the Juubi.
The main characters could potentially be a new set of ninjas created specifically for this fanfic. They might be a group with a special connection to nature and the forest. Maybe there's a young ninja who discovers an ancient scroll that holds the key to creating the forest. Alongside this young ninja, there could be an old and wise mentor - like figure who guides them through the process of bringing the forest to life. Another possibility is that it could involve some of the minor characters from the Naruto series who are given more prominence in this fanfic, such as the forest - dwelling clans that we don't see much of in the original story.
It could feature new characters created specifically for this fanfic. Maybe there's a hermit who has been living in the area where the forest is born and has some knowledge about its secrets. Or perhaps a young ninja from a small village nearby who discovers the forest first and then gets involved in a bigger adventure related to it. However, it's also possible that it mainly focuses on well - known Naruto characters like Sasuke or Sakura, who might have different roles in relation to the forest's birth, like Sasuke using his Sharingan to uncover some hidden truth about the forest.
In a 'birth in elevator' fanfic, the main characters would likely include the pregnant woman. Her partner, if he is also in the elevator, would be another main character. And then there could be a random stranger in the elevator who has some sort of medical or emergency response training. This person could step up and help with the birth, making them an important main character in the story.
Since I haven't read the 'eye of the fire dragon fanfic', I can't say for sure who the main characters are. But it could be a dragon - keeper, a brave knight, or a powerful wizard.
Well, there could be the dragon lords. One might be a powerful fire dragon lord who is fierce and protective of his kind. And on the ice side, a wise ice dragon lord who is known for her strategic thinking.
Well, it could be a young hero, perhaps named Alex, who has a special ability like being able to control fire. Alex might be on a journey to discover the truth about the castle.
There could be a whole new set of characters in the 'naruto frozen fire fanfic'. It might be a group of rogue ninjas who have discovered the secret of frozen fire and are using it to their advantage. Or it could be a young apprentice who is learning to control this strange power under the guidance of an old sage. Without reading the actual fanfic, it's all speculation though.