In the world of the Middle Ages, demons were seen as servants and helpers of the devil, who tempted people to sin and thus brought them to hell to perpetual torment, and of whom people were literally afraid of hell. Hardly any Central European in the 21st century would admit to believing in the existence of demons. Things looked very different 500 years ago: The population of the Middle Ages and the early modern period was convinced of the existence of devils, witches and their demonic assistants. Weather demons brought storms, crop failures and conflagrations, disease demons swept away the population, demons tormented poor souls in hell and tempted people to sin. The fact that these adversities could not only happen at the behest of the devil, but also with God's tolerance, made the demonic threat omnipresent. Only God - mostly through the intercession of his saints - could temporarily stop the activities of the demons. Based on medieval texts, pictorial sources and sculptures, with recourse to the Old and New Testament, Simek explains what medieval people imagined the devil, demons and witches to be, what they looked like, what they did and how to protect oneself from them sought.