The uninvited guest in "The Masque of the Red Death" is the mysterious stranger who appears among the revellers after they had been isolated in Prince Prospero's castle for several months. Suddenly, he was simply there. His appearance was hideous:
The figure was tall and gaunt and shrouded from head to foot in the habiliments of the grave. The mask which concealed the visage was made so nearly to resemble the countenance of a stiffened corpse that the closest scrutiny must have had difficulty in detecting the cheat . . . . the [figure] had gone so far as to assume the type of the Red Death. His vesture was dabbled in blood--and his broad brow, with all the features of the face, was besprinkled with the scarlet horror.
This guest seemed to be the embodiment of the deadly disease the revellers were attempting to escape. He appeared among them looking like a corpse, covered with blood, and he moved among them "with a slow and solemn movement." He is a spectral, ghostly image of death who inspires shuddering and terror in those who look upon him.
In some ways the Red Death is much like the Bubonic Plague that wiped out most of Europe in the 14th Century. He, "The Red Death," is the embodiment of inescapable destruction. There were many rich, powerful people like Prospero during this bleek period of history who felt they could escape the Black Death. The Red Death is not a "real" person, per say, but the symbol of destruction. No one in the end can escape death no matter how hard they may try.