Well, obviously the mountain man himself is a very important character. He is the central figure around which the whole story revolves.
John Grimes is a very important character. He is the protagonist and his journey of self - discovery is central to the story. His father Gabriel is also important as he has a significant influence on John's life and the family dynamic. Elizabeth, John's mother, is another key figure as her relationship with both John and Gabriel shapes much of the narrative.
Then there are the characters in the ranch where they work. For example, the boss who hires them on Brokeback Mountain. These minor characters help to set the context of the story, showing the kind of working environment and the social environment in general that Jack and Ennis are part of.
The invisible man himself is the most important character. He is the narrator and his journey forms the core of the story. Then there is Dr. Bledsoe, who represents the authority within the black community but also has his own self - serving motives.
The invisible man himself is of course the most important character. He is the one through whose perspective we see the story unfold.
Obviously, the old man himself is a very important character. He is the central figure around which the story revolves.
Tony Stark is the most important character. He is the one who creates the Iron Man suit and becomes the superhero. Pepper Potts is also important as she is Stark's assistant and has a close relationship with him.
One of the key characters is Captain Bluntschli. He represents the reality of war, being a professional soldier who is more concerned with survival than glory. Then there's Raina Petkoff, a young woman who has an idealized image of war and love at the beginning. Her father, Major Petkoff, is another important figure, as his character also reflects the values and attitudes of the society in the novel.
I'm not sure exactly who the important characters are without reading the novel. But typically, there would be a protagonist who drives the story forward. There might also be a mentor - like character who guides the protagonist in some way.
The central character is the Invisible Man. His character development from an ordinary person to one with the power of invisibility and how he copes with it is key. There are also the scientists he might have come across. They play a role in either trying to understand his condition or fearing it. And the people in the places he hides or tries to live among, they all add to the story.
The wolf man himself is obviously a very important character. He is at the center of the story, driving the plot forward with his actions and his struggle with his identity.