Nathan, in his human form, is either 18 or 19, has long scraggly black hair that goes down to his shoulders, a silver ear ring in one ear, and a fake tattoo of a bat on his right hand. Nathan (in his snake form) is a rare breed of cottonmouth viper.
Nathan has a relaxed attitude. This changes when Boone goes into the laboratory; Nathan's personality becomes near-robotic, and he begins saying things such as: "it doesn't hurt" and "just cooperate." When Boone tries to escape, Nathan tackles him to the ground. Throughout the book, Nathan proves that he has a tendency to lie: Nathan lies about Roddy leaving, he also lies about the cottonmouth in his bed, and he lies about the secret laboratory.