"In the western or black chamber the effect of the firelight that streamed upon the dark hangings through the blood-tinted panes, was ghastly in the extreme..." (Poe 430).
The setting is considered to be gothic and somber due to the diction used such as secluded, voluptuous, black, dark, etc.
Symbolism:The guest who is dressed in red and as a corpse symbolizes the plague.
The new guest symbolizes the plague
because it symbolizes death.
"He is not my master. Death has no master" (Poe).
Death is the uninvited guest.
The center of the whole plot is death and the use of the word death also has an effect on the mood. Nobody relates death with happiness and joy. Death is sad, and sorrowful.
"And, then, they recognized the presence of the" Red Death ", He had arrived like a thief in the night, and, one by one, the cheerful rakes fell through the rooms of the orgy, flooded with a bloody dew" (Poe).