The demonic landscape of Ferdowsi’s Shahnameh is fantastic and varied. The epic begins with an account of the demon Ahriman’s attack against Gayumart, first king of the world. As it continues, we encounter numerous other stories about battles between humans and demons, from Kay Kavus’ ill-advised plan to attack the demon land of Mazandaran to Rustam’s combat with the Akvan Div. But the boundary between the human and the demonic in the Shahnameh is not clearly drawn. As Dick Davis has observed, Rustam has a “tangential relationship” with humanity, and his connection to the supernatural—which manifests itself in his use of trickery and magic—is inherited through demonic ancestry. This paper examines the intersections between human beings and the demonic in the Shahnameh, specifically the way in which serpentine imagery and the use of sorcery and guile blur the line between the two categories. My study begins by examining the import of Zahhak’s transformation from Arab prince to serpent-shouldered demon king. I demonstrate how disparate notions of the demonic converge in this pivotal character, whose encounter with Iblis marks the first time a human being is tempted by a demon in the Shahnameh. I also note the manner in which Zahhak functions as a liminal figure through whom demonic traits are passed to posterity, including Rustam. In tracing subsequent occurrences of serpentine imagery and examining trickery and magic as traits occupying a borderland between human beings and demons, I highlight the gendered nature of demonic representations in Ferdowsi’s epic. Informed by the work of Mahmoud Omidsalar on women’s roles in key junctures of the Shahnameh narrative as well as by Kinga Markus-Takeshita’s observations on women and folklore in the epic, I contrast the uniformly negative depictions of females who use magic with the varied portrayals of males who do the same. In addition, I note the relationship between the feminine and the serpentine in the cases of Rudabeh and Haftvad’s daughter. In so doing, I show the way in which the demonic adds layers of ambiguity to characters throughout the Shahnameh, ultimately serving to complicate the notion of evil itself.