Growing interest in tantric Buddhism worldwide has resulted in an explosion of literature on the subject; despite this, there still remain many voids in our understanding of this complex practice, with its proliferation of gods and saints, bodhisattvas and demons. R. H. van Gulik was one of the pioneer Western scholars of the tantric deities, having completed a highly acclaimed doctorate on the subject of the tantric god, Hayagriva, in 1935, with the dissertation upon which this book was based. Soon out of print, it seems that no monograph has since been published on the subject, despite the relatively frequent occurrence of the 'The Horse-Headed One' both in Buddhist practice and in religious painting and sculptured images, across Asia. In Hayagriva: Horse Cult in Asia, van Gulik traces the evolution and migration of the god, from its ancient roots in Hindu belief, through its adoption into the Tibetan Buddhist pantheon, and the subsequent migration of its cult westward, through Mongolia and China to Japan. In this long journey, Hayagriva interacted with indigenous, pre-Buddhist horse cults and assumed various attributes as a result, ranging from a deity who conferred fertility, to protector of the faithful from demons, to mythical winged navigator of the vast northern plains.