Final answer:
Without the specific text 'Darkness in the Desert' by Morena Sommers, we cannot determine the unique theme of the work. Common literary themes related to darkness include isolation, human nature, and struggle against adversity.
Step-by-step explanation:
"Darkness in the Desert" by Morena Sommers is not specifically referenced in any of the provided excerpts, making it challenging to determine the theme of this text. However, we can explore common themes related to darkness and desolation that appear in literature. Themes often depict isolation, the duality of human nature, and struggle against adversity. These themes are showcased in various works such as Stephen Crane's "In the Desert", where the narrator encounters a creature that eats its own heart, symbolizing self-destruction and introspection, and in the descriptions of the Utah uplands, which evoke feelings of loneliness and contemplation.