How is "The Masque of the Red Death" an allegory?
The allegorical nature of Poe's short story is apparent with the symbolically named Prince Prospero, who is the only character that is named; further, the conflict of this protagonist is also symbolic as Prospero battles death in a conflict that produces a moral lesson.
When Prospero learns of the plague, he gathers together his noblemen and their ladies into an abbey-fortress in a willful effort to establish a bastion against death.
With such precautions the courtiers might bid defiance to contagion. The external world could take care of itself.
Within the fortress, are seven rooms, symbolic, perhaps, of the seven stages of man. In a hall, the presence of time is marked by a large clock that menacingly tolls the hour. While each of the rooms is a different color with windows stained to match and no one room can look into another. They are described as representative of life:
There was much of the beautiful, much of the wanton, much of the bizarre, something of the terrible, and not a little of that which might have excited disgust. To and fro in the seven chambers there stalked, in fact, a multitude of dreams.
The last room is the most forbidding and moribund as it is "shrouded" in black tapestries of heavy velvet cloth, not only on the wall, but on the ceiling, as well. Clearly, this room is the room of death,
But in this chamber only, the color of the windows failed to correspond with the decorations. The panes here were scarlet—a deep blood color.
It is into this room of darkness and death that an intruder enters. Incensed that someone of such audacity should force his way into his magnificent revel, the Prospero, who symbolizes the wealthy and powerful, accosts the intruder in order to eject him from his fortress. Instead, this messenger of the red death embraces the prince, who succumbs to a power that no wall can deter.