What "single effect" do you think Poe intends to create in "The Masque of the Red Death"?
The intended effect of the story is a feeling of horror. The first paragraph introduces this tone with Poe's detailed description death from the "pestilence" known as the "Red Death." It is "hideous" with "the horror of blood," including "profuse bleeding at the pores" and "scarlet stains . . . especially upon the face of the victim." Blood (and the color of blood) function as a major motif in the story; Poe establishes it immediately and returns to it again and again. For instance, the windows in the final chamber are "a deep blood color."
The appearance of the mysterious masked figure intensifies the sense of growing horror in the story. He is tall and emaciated and "shrouded from head to foot in the habiliments of the grave." His face is that of a "stiffened corpse" and is so real in appearance it is difficult to distinguish it from that of a real corpse. His clothing and face are "dabbled" and "besprinkled" with blood, "the scarlet horror." When they attack the repulsive figure, Prospero's guests find "in unutterable horror" there is no physical body beneath the robe or the mask. The story ends in the final horror: "And Darkness and Decay and the Red Death held illimitable dominion over all."