As faithful as "House of Usher" was to the spirit of Edgar Alan Poe, "Masque of the Red Death" is the very opposite. Fantastic sets, a great use of color and some very pleasing widescreen compositions cannot hide the fact that this has little to do with the short story that supposedly inspired it. Even worse, Roger Corman seems to have felt, on the heels of Usher's great success, that the more superficial Poe references he could cram in an hour and a half the better which leads to the film featuring (for no artistic reason whatsoever) a clock with a double-bladed pendulum, a royal dwarf named Hoptoad and his revenge, a gorilla (costume) and several black crows.
AIP's aping of the Hammer formula (even going so far as to give Hazel Court a lead role here) via Edgar Alan Poe is already on a downward slide here, and subsequent incursions would be of significantly reduced quality, even falling into the real of self parody. As a stand alone film it might be effective, but as an adaptation of Poe's greatest work it was most disappointing.
Three stars for Vincent Price (far creepier as the Red Death than Prospero), the gorgeous sets, the use of color and the dance of death sequence that climaxes the movie.