Medieval scholars tried to count every demon, and loved the number six
In 1467 Alonso de Espina announced that there were exactly 133,316,666 demons. A century later Johann Weyer counted 4,439,622, sorted into 666 legions of 6,666 each under 66 rulers. The repeated sixes were no accident: both men were building on the number of the beast in the Book of Revelation.
Christian demonology grew from scripture, early Christian writers and borrowed legends into an elaborate field, studied most deeply in the Roman Catholic Church. In tradition demons are fallen angels, and Espina's huge figure seems to rest on reading Revelation 12 as saying a third of the angels fell. Their knowledge was considered specialised rather than total, and their power limited to what God permits. The Book of Enoch, canonical today only in the Ethiopian and Eritrean Orthodox churches, offered another origin: the spirits of giants born to angels and humans.
Writers argued over basic questions. Gregory of Nyssa in the 4th century believed demons came in male and female forms and could reproduce; others held their number fixed. Basil of Caesarea suggested demons built temporary bodies by condensing vapour and animating them like puppets, and Henry More later reasoned that this explained why such bodies were said to feel cold. Ambrogio de Vignati disagreed entirely, insisting demons could not form bodies and that sightings were hallucinations.
Their look changed over time. Scripture says Satan can disguise himself as an angel of light, but demonologists usually described monstrous beings, and painters from Hieronymus Bosch to Francisco Goya took up the theme. Horns may come from the beasts of Revelation 13 and from ancient gods like Moloch, shown with bull features. Chaucer linked the Devil with green; red came later.
Even the Catholic Encyclopedia regarded much of the subject with suspicion, summing up faulty demonology in a Latin line saying it is taught by demons, teaches about demons, and leads to demons.
Source: Christian demonology
