This book explores the liturgical significance of Theophany and Theophany-Deesis imagery in Eastern Christian sanctuaries, with a special focus on medieval Lebanese examples. It reveals how these sacred apsidal images visually enriched the eucharistic liturgy, bringing Christ, angels and saints into the heart of worship. Drawing on rare unpublished evidence, this study illustrates how these depictions bridge earthly and heavenly liturgies, transforming the spiritual experience and theological understanding of both clergy and the faithful. By challenging traditional views, the book also highlights the vibrant cultural interactions between East and West that shaped the religious and artistic traditions of the medieval Mediterranean world.