Examining the history of altar decorations, this study of the visual liturgy grapples with many of the previous theoretical frameworks to reveal the evolution and function of these ritual objects. Using an interdisciplinary approach, this book uses traditional art-historical methodologies and media technology theory to reexamine ritual objects. Previous analysis has not considered the in-between nature of these objects as deliberate and virtual conduits to the divine. The liturgy, the altarpiece, the altar environment, relics, and their reliquaries are media. In a series of case studies, several objects tell a different story about culture and society in medieval Europe. In essence, they reveal that media and media technologies generate and modulate the individual and collective structure of feelings of sacredness among assemblages of humans and nonhumans. The book will be of interest to scholars working in art history, medieval studies, early modern studies, and architectural history.