Scobie is an important character. He is a police officer and his actions and decisions drive much of the plot.
Helen is a significant character. She has a relationship with Scobie and her presence complicates his life and moral choices. There is also Wilson, who has his own motives and is involved in the web of events in the story.
I'm not sure specifically as I haven't read this exact novel. But usually, there is a protagonist who the story mainly focuses on. This character is likely to be someone with a complex personality and a lot at stake in the plot.
I'm not sure specifically as I haven't read it. But usually in a novel, the main characters are those who drive the story forward. It could be a protagonist who is on a journey, either physical or emotional, and the people around them who either help or hinder that journey.
Marlow is a very important character. He is the narrator of most of the story and his journey into the heart of Africa forms the core of the narrative. Kurtz is also crucial. He is a man who has gone deep into the Congo and has been corrupted by the power and the environment there. The Manager is another important character. He is in charge at the Company's station in the Congo and is often in conflict with Marlow and represents the more bureaucratic and self - interested side of the European presence in Africa.
I'm not sure specifically as we don't have more details about this 'The Dark Heart Novel'. But generally, there could be a protagonist who is on a journey to understand or overcome his or her 'dark heart'. There might also be a mentor - like figure who helps the protagonist in this exploration.
Reuben Butler is an important male character. He is a love interest for Jeanie and his own moral and intellectual qualities play a role in the story. He also represents a certain type of man in that society, one who is trying to make his way through education and good deeds.
Without reading it, it's hard to say. But it could feature the main RWBY characters like Ruby, Weiss, Blake, and Yang, as they are often the focus in RWBY - related fanfictions.
Mick Kelly is also significant. She is a young girl with big dreams and a passion for music. Her relationship with Singer is quite complex.
Marlow is a very important character. He is the narrator who takes us on the journey into the heart of darkness. Kurtz is also crucial. He is a man who has become corrupted by the power and isolation in the Congo. Then there are the native Africans, though they are often not given as much individual depth, they play a significant role in representing the 'other' in the context of the colonial story.
The most important character is Marlow. He's the one who undertakes the journey up the Congo River and has all the encounters that form the basis of the story. Kurtz is another significant character. He has a sort of magnetic pull on Marlow and represents the extreme of what can happen to a man in that environment. Additionally, the Manager of the trading post is an important character as he is part of the power structure in the Congo and his actions and motives contribute to the overall atmosphere of the story.
The protagonist is surely an important character. His inner world forms the core of the story, so understanding his personality, motives and growth is key.