Another Theory I forgot I had was that the teacher created the Main Character. That we are a human created through alchemy. The Witch creates monsters and teacher knows about the werewolves, it is possible he knows of the witch and took a favor from her creating a son, aka the main character. The main character also calls his teacher Master often, despite having learned nothing from him at the start of the game. I'm thinking we were literally created to be a servant, but teacher got cold feet, or went to complete his favor. Think about it, no one knows where the main character came from, and only Gunnar talks about you appearing from nowhere and being an extremely capable person. Where are we from? We were made.
That theory also crossed my mind; however, to connect it with my other theory of the teacher being a part of the Bentley family, what if we are too? Remember, people don't know much about that family as they prefer to live in isolation. Only a few members are known to exist, as mentioned by the Quartermaster who also stated that they don't know if Lord Salvador has any children. What if we are one of his children? Did our teacher kidnap us? Were we abandoned by the family and then found by our teacher? Or did Lord Salvador entrust our teacher to take care of us in an attempt to save us, knowing that someone...
or something would come to take the entire Bentley family?
Then after our teacher discovered that the family had vanished, he went to investigate what had happened to try and help our real father. For now, we actually don't know if he's still alive; he's probably been taken as well. Our MC, who's prolly the last of his bloodline, will be the one to save everyone...
I had so much fun writing this xD!