I don't know for sure since I haven't read it. But typically in such a novel, there might be a curious protagonist who is drawn to the spiral staircase, perhaps a young person full of inquisitiveness.
There could be an old caretaker or owner of the building with the spiral staircase. This character might hold a lot of knowledge about the place and the staircase, and their interactions with the other characters could be crucial to the plot. There may also be a villain - like someone who wants to keep the secrets of the staircase hidden and will go to great lengths to stop the protagonist from uncovering them.
I'm not sure specifically as I haven't read it in detail. But often novels with a 'spiral staircase' in the title might deal with themes of mystery, perhaps something hidden or a journey of discovery related to the staircase.
Once, I entered an old mansion. In the center was a spiral staircase. As I climbed, the air grew colder. Whispers seemed to follow me. At the top, a figure in white flashed by. I ran down, but the stairs seemed endless. My heart pounded as I finally reached the bottom, vowing never to go near that spiral staircase again.
Since we don't have much information about this 'time spiral novel', the main characters could be ordinary people who get caught up in the time - spiraling events. They might start off as normal individuals living their regular lives, but then as the time - spiral begins to affect their world, they develop unique abilities or characteristics related to dealing with time. For example, one character could be able to remember fragments of different time loops, which helps them try to break free from the spiral or understand it better.
I'm not entirely sure, but there might be a teacher as one of the main characters. Teachers are often central in novels set in educational settings as they interact with a variety of students.
Since I don't know the exact details of the story, the main characters could be those directly involved in the events around the staircase. It might be a detective if there's a crime involved, the person who built the staircase, or those who witnessed something strange on the staircase.
Since I don't know the exact 'the staircase original story', I can't say for sure. But it could have a protagonist who is a homeowner or tenant who discovers something strange about the staircase.
The main character is the man who was accused of the crime. And of course, his wife, who was the victim. Their relationship and the events surrounding their lives are central to the story.
I'm not certain specifically. But it might include planeswalkers, as they are often central characters in Magic: The Gathering stories.
The never - ending feeling. You keep climbing or descending, but it seems like you're not getting anywhere. It's like being trapped in a loop of fear.
It's hard to say for sure without reading it, but it could still be Bella, Edward, and Jacob. Since it's a Twilight fanfiction, they are likely to be important. Maybe it focuses on how they react when things start to go wrong in the downward spiral.