This may be a bit late to be of help, but in case anyone else out there wants some help with characters' contributions to the novel here are a few examples:
The Russian: The Russian is a devoted follower of Kurtz who is described by Marlow to look like a Harlequin because of the colorfully patched outfit he is wearing. Marlow depicts him as having “a beardless, boyish face, very fair, no features to speak of, nose peeling, little blue eyes, smiles and frowns chasing each other over that open countenance like sunshine and shadow on a wind-swept plain” (131). He is simple-minded and ridiculous in nature, and possesses an innocence in which he has “no more idea of what would happen to him than a baby” (132). The Russian becomes morally blind to Kurtz’s evil actions, yet he is not malevolent himself. He merely watches the events take place, yet is one of few whites who is not a rogue. The main purpose of the Russian is that he is the fool of the novel. He serves to supply information about Kurtz that neither Marlow nor the reader knew before. This places him in the traditional role of the fool throughout literature. The fact that he is Russian is important because he is able to supply information that differs from the imperialist nations—for Russia did not practice colonialism. He remains with Kurtz because he believes Kurtz has taught him well.
The General Manager: The Manager is described by Marlow as “commonplace in complexion, in feature, in manners, and in voice. He was of middle size and of ordinary build. His eyes, of the usual blue, were perhaps remarkably cold, and he certainly could make his glance fall on one as trenchant and heavy as an axe” (89). The Manager stands as a general image of the villain of the novel. He is representative of the greedy bureaucrats who want nothing more than the success of the business, even at the cost of the enslavement of the Africans. His lack of sympathy for the “savages” portrays him to be an unlikable man, one who cares not for the well-being of others. He is described as inspiring “neither love nor fear, nor even respect” (89), but “uneasiness”. What’s more, he lacks talent and intelligence and only holds his position because he has the ability to remain healthy in the jungle while many others become sick. He dislikes Kurtz and Marlow because he believes both to be threats to his position, and as a result he sabotages Marlow’s boat in an attempt allow Kurtz to die before they arrive to save him. On the journey to Kurtz, the manager practically starves the African cannibals on board and feels no sympathy in doing so. He seems to be perfectly heartless, possessing no shame or pity for his actions. It is for this reason that he appears to Marlow to be the worse of the two evils (Kurtz being the second evil). The manager simply maintains the routine without any morals at all. Kurtz has misguided morality, while the general manager is a moral vacuum.
The Intended: She is the woman Kurtz was engaged to be married to. When Marlow first meets the Intended she is dressed entirely in black and “[floats] towards [him] in the dusk” (160). She is described as having “a mature capacity for fidelity, for belief, for suffering” (160), and seems “surrounded by an ashy halo” (160). It has been over a year since Kurtz’s death, and yet the Intended continues to mourn for him. Marlow seems to think that she will remain in mourning forever, and that for her Kurtz died only yesterday. Although she is saint-like in her appearance her grieving seems over the top. This fits Marlow’s opinion of women, for he believes them to be unrealistic. The Intended still holds the ideal that Kurtz was generous, kind, and noble in nature. She grasps this ideal with all of her heart because she needs to believe that Kurtz died for a worthwhile cause. Since we can assume Kurtz went into the Congo in order to provide a better life for the two of them, the Intended probably needs this reassurance so that she can relieve some of her guilt. Although Marlow hates a lie, it seems as though the Intended is almost begging for him to tell her one. When he unintentionally mentions that he was with Kurtz when he said his last words, the Intended aches to know what they were. Marlow lies to her and says that Kurtz pronounced her name as the very last thing he said, and she happily exclaims, “I knew it—I was sure!” (164). This portrayal of Kurtz’s Intended is common of the Victorian woman. She is shown as naïve and secluded from the truth. According to Marlow, this is necessary so that women can maintain their beauty without being exposed to the evils of the world. Like much of civilization, the Intended remains tragically devoted to Kurtz, unaware of the evils he has committed, and the horrors which have taken place.