Tantric traditions in both Buddhism and Hinduism are thriving throughout Asia and in Asian diasporic communities around the world, yet they have been largely ignored by Western scholars until now. This collection of original essays fills this gap by examining the ways in which Tantric Buddhist traditions have changed over time and distance as they have spread across cultural boundaries in Asia. The book is divided into three sections dedicated to South Asia, Central Asia, and East Asia. The essays cover such topics as the changing ideal of masculinity in Buddhist literature, the controversy triggered by the transmission of the Indian Buddhist deity Heruka to Tibet in the 10th century, and the evolution of a Chinese Buddhist Tantric tradition in the form of the True Buddha School. The book as a whole addresses complex and contested categories in the field of religious studies, including the concept of syncretism and the various ways that the change and transformation of religious traditions can be described and articulated. The authors, leading scholars in Tantric studies, draw on a wide array of methodologies from the fields of history, anthropology, art history, and sociology. is groundbreaking in its attempt to look past religious, linguistic, and cultural boundaries.