In the later stages of the story Old Nick's physical appearance is developed through the revelation of scars and tattoos on his body. When Ma is trying to find a way to escape, she notices a tattoo on Old Nick's arm and wonders if it might be a clue to his identity. She also notices scars on his back, which suggest a violent past. These details add complexity to Old Nick's character and further emphasize the danger that he poses to Jack and Ma. Overall, the physical appearance of Old Nick is developed through a combination of details such as his size, strength, smell, voice, clothing, scars, and tattoos. These details create a vivid and menacing picture of his character, emphasizing the fear and danger that he poses to Jack and Ma.