It's possible that Lumentor is a non - human magical being in the fanfiction. For example, they could be a spirit or a creature with unique powers. Their presence in the Harry Potter universe through the fanfiction could disrupt the normal order of things and lead to all sorts of new adventures and challenges for the beloved characters of the original series.
Perhaps a Lumentor Harry Potter fanfiction focuses on Lumentor being from a different magical dimension. They accidentally end up in the world of Harry Potter. Lumentor then has to navigate the complex politics and magic system of Hogwarts while also trying to find a way back home. This type of fanfiction can introduce new magical concepts and cultures from Lumentor's dimension, making it a very unique take on the Harry Potter universe.
Another possible betrayer could be Dumbledore in some darker fanfictions. He might have a hidden agenda all along. He could be using Harry as a pawn in a much larger and more sinister game. And when Harry starts to figure things out and goes against Dumbledore's plans, Dumbledore betrays him to keep his own plans on track.
Maybe some of the Hogwarts professors like Professor Sprout. After all, she's the Herbology teacher. She could give Harry some expert advice on how to grow different kinds of food plants. She might even let him use some special greenhouses or tools in the school for his food - growing projects.
Minerva in Harry Potter fanfiction is often the same strong, intelligent, and strict character as in the original books. She is a Transfiguration teacher at Hogwarts.
Goldstein in Harry Potter fanfiction could be a new character introduced to add more depth to the existing story. They might be related to some important wizarding families or have a special connection to a particular magical object or place. For example, they could be a descendant of a famous wizard who once had a role in Hogwarts' history. Sometimes, Goldstein is used as a character to explore different aspects of the wizarding world that the original books didn't cover much, like a different form of magic or a unique sub - culture within the wizarding community.
In 'Harry Potter' fanfiction, Blackfire might be a character created to add more depth and complexity to the story. She could be a shapeshifter, for example. This ability would allow her to infiltrate different groups in the wizarding world, either for good or bad purposes. Her character can be used to explore different themes such as loyalty, identity, and the nature of magic that weren't fully explored in the original books.
Another possibility is that Cadmus is a character who has a connection to a prophecy related to Harry. Maybe he is the one who discovers the prophecy or has some knowledge about it that he shares with Harry at a crucial moment. This could set off a chain of events that changes the course of Harry's battle against Voldemort in the fanfiction.
In Harry Potter fanfiction, Metawitch could be an original character created by the author. She might be a witch with extraordinary powers that are different from the normal magic we see in the original books. For example, she could have the ability to manipulate time in a more complex way than Hermione's Time - Turner.
His friends from Hogwarts, like Ron and Hermione, are likely to help. Ron could bring his family's practical knowledge of wizarding homes and Hermione would contribute with her extensive research skills.
In my opinion, Dumbledore would still be a great headmaster in fanfiction. His wisdom and experience are invaluable. He always had a deep understanding of the students and was able to guide them through difficult times. He also had a great sense of humor and was very approachable despite his great power.