According to Robinson, the design of the beast, which he nicknamed "Humphrass", was based on a wingless hangingfly. In order to create the creature's skeletal form, Robinson added aluminum stripping to a plywood base, then covered the frame with chicken wire before wrapping it in sheets and muslin. He then soaked the frame in vinyl paint in order to waterproof the design, since it had to be used in the snow. The creature's head was fashioned out of quarter-inch aluminum wire, which was then encased in steel wire and wrapped in muslin. The creature's fangs and teeth were also constructed with aluminum wire. Robinson then placed putty and patches of crepe hair onto the design before adding spun glass in order to give it a cobwebby appearance.