The monograph explores the meaning and role of Melchizedek and Melchiresac in Judaism of late antiquity. In Part I four texts from Qumran are transcribed from the published photographs and translated: 11QMelchizedek, 4Q'Amramb, 4QṬeharot D, and 4QBerakot A. The commentary focuses on establishing the reading of the texts and restorations made on the basis of parallel biblical passages and other writings among the Dead Sea Scrolls. Part II examines the role of the heavenly Melchizedek in the Qumran literature, particularly in relation to his evil counterpart, Melchiresac. These two figures serve as opposing angels who act as leaders of the earthly and heavenly kingdoms of the sons of light and the sons of darkness. Certain Zoroastrian religious concepts that were well known before the second century B.C.E. and that parallel the Essene belief in the spirit-leaders of the worlds of light and darkness are also investigated. Part III discusses the influence of the heavenly Melchizedek on the Johannine concept of the Paraclete, on the comparison between Christ and Melchizedek in the NT letter to the Hebrews, on the NT Son of Man, and on the identification of Melchizedek with the angel Michael.