The catechetical compilation Kitab al-Idah ("The Book of the Elucudation") of the tenth-century Coptic bishop and theologian Sawirus ibn al-Muqaffa' is one of the most frequently copied theological texts of the Arabic-speaking Coptic Church. While its first eight chapters deal with the principal doctrines and practices of the faith, Chapter Nine-omitted from the most recent printed edition of the work-must be understood against the backdrop of the flourishing speculation about supernatural beings and the afterlife that has long characterised Egyptian religion, including Coptic Christianity. In this chapter Sawirus responds to a homily, attributed to Theophilus of Alexandria, on the Angel of Death: the reason for his being granted authority over humankind, and the day of his feast. With considerable passion, Sawirus refutes this homily with arguments drawn from common sense, science, scripture and theology; for him, the cult of the Angel of Death is nothing but a ruse of Satan. However, Sawirus does not simply dismiss Egyptian Christian concern about the realm of supernatural beings. Instead, he attempts to absorb this realm more completely into the world of the Bible by summarizing or redescribing the Bible's central story as that of Christ's deception of and victory over Satan and his demonic host. While this narrative is rooted in ancient soteriological tradition, Sawirus' rendering is fresh and entertaining. The popularity of the Kitab al-Idah suggests that many generations of Egyptian Christians found it not merely entertaining, but genuinely elucidating.