The fifth level was reserved for whatever animal Humperdinck would one day capture that would ultimately prove most dangerous.
Prince Humperdinck (Chris Sarandon in the movie) keeps a menagerie that he calls “The Zoo of Death.”
Inside, Humperdinck keeps the world’s most dangerous animals in a death maze that included five levels.
The first was filled with Earth’s fastest creatures, the second with the strongest, the third with the most poisonous and the fourth with the most dangerous “enemies of fear”.