This article examines Rangda and her role as a chthonic and mythological figure in Bali, particularly the way in which Rangda’s identity has intertwined with that of the Hindu goddess Durga— slayer of buffalo demons and other creatures that cannot be bested by Shiva or other male Hindu gods. Images and stories about Durga in Bali are significantly different from those found in Hindu contexts in India. Although she retains the strong-willed independence and decision-making capabilities prominently associated with Durga in India, in Bali the goddess Durga is primarily associated with violent and negative attributes as well as looks and behaviours that are more usually associated with Kali in India. The reconstruction of Durga in Bali, in particular the integration of Durga with the figure of the witch Rangda, reflects the local importance of the dynamic relationship between good and bad, positive and negative forces in Bali. I suggest that Balinese representations of Rangda and Durga reveal a flux and transformation between good and evil, not simply one side of a balanced binary opposition. Transformation—here defined as the persistent movement between ritual purity and impurity—is a key element in the localization of the goddess Durga in Bali.