Answer :
The author includes the sentence to foreshadow future events, emphasizing the intensity and peculiarity of the protagonist's dream to underline impending significant developments in the story.
The author's purpose for including the sentence 'It was unusual as a dream because it was full of smells, and he never dreamt smells' is to foreshadow future events. Dreams in literature often serve as a mechanism for indicating future possibilities or stirring intrigue about what is to come, especially when the dream deviates from the character's usual experiences. In the context provided, the dream signals an element of alterity or otherness, which resonates with the protagonist's anxieties and the overarching sense of foreboding within the narrative. By evoking strong sensory details such as smell, which is deeply tied to memory and often difficult to articulate, the author is underscoring the intensity of the protagonist's experience. This narrative decision enriches the story's ambiance and prepares readers for a significant development related to these newfound sensory impressions.