The Martian Erloors are humanoid bat-like creatures with membranous wings and glowing eyes. Despite being almost the size of a man, and having wings that have somewhat degenerated to allow the development of hands at the tip, the creatures are still capable of flight owning to the weaker gravitational attraction of Mars. In addition to their hands, their feet are also prehensile, allowing them to hang on tree branches with relative ease. They appear to be strictly nocturnal.