Known as the Black Primordial, Diablo, or Noir, has a distinctive appearance. His black hair is streaked with red and gold, and his eyes are golden with red pupils and black sclerae. His outfits are dominantly black, he initially wore aristocratic garments, which were replaced by a butler outfit following his naming and subsequent evolution to a Daemon Lord.
This minimal change in his appearance underscores his enduring nature with the color black standing out from his head to toe, consistent with his 'Primordial Black' title.