Traditions about the Kallikantzaroi vary from region to region, but in general they are half-animal, half-human monsters, black, hairy, with huge heads, glaring red eyes, goats' or asses' ears, blood-red tongues hanging out, ferocious tusks, monkeys' arms, and long curved nails, and commonly they have the foot of some beast. "From dawn till sunset they hide themselves in dark and dank places .., but at night they issue forth and run wildly to and fro, rending and crushing those who cross their path. Destruction and waste, greed and lust mark their course." When a house is not prepared against their coming, "by chimney and door alike they swarm in, and make havoc of the home; in sheer wanton mischief they overturn and break all the furniture, devour the Christmas pork, befoul all the water and wine and food which remains, and leave the occupants half dead with fright or violence." Many like or far worse pranks do they play, until at the crowing of the third cock they get them away to their dens. The signal for their final departure does not come until the Epiphany, when the "Blessing of the Waters" takes place. Some of the hallowed water is put into vessels, and with these and with incense the priests sometimes make a round of the village, sprinkling the people and their houses.
Besides this ecclesiastical purification there are various Christian precautions against the Kallikantzaroi - e.g., to mark the house-door with a black cross on Christmas Eve, the burning of incense and the invocation of the Trinity - and a number of other means of aversion: the lighting of the Yule (= Christmas time) log, a large log of wood called a skakantzalos, the burning of something that smells strong (sometime the Greeks will also burn old shoes, the smell of which keeps the wicked elves away), and - perhaps as a peace-offering - the hanging of pork-bones, sweetmeats, or sausages in the chimney.
Just as men are sometimes believed to become vampires temporarily during their lifetime, so, according to one stream of tradition, do living men become Kallikantzaroi. In Greece children born at Christmas are thought likely to have this objectionable characteristic as a punishment for their mothers' sin in bearing them at a time sacred to the Mother of God. In Macedonia people who have a "light" guardian angel undergo the hideous transformation.
Many attempts have been made to account for the Kallikantzaroi. Perhaps the most plausible explanation of the outward form, at least, of the uncanny creatures, is the theory connecting them with the masquerades that formed part of the winter festival of Dionysus and are still to be found in Greece at Christmastide. The hideous bestial shapes, the noise and riot, may well have seemed demoniacal to simple people slightly "elevated," perhaps, by Christmas feasting, while the human nature of the maskers was not altogether forgotten. Another theory of an even more prosaic character has been propounded that the Kallikantzaroi are nothing more than established nightmares, limited like indigestion to the twelve days of feasting. This view is taken by Allatius, who says that a Kallikantzaros has all the characteristics of nightmare, rampaging abroad and jumping on men's shoulders, then leaving them half senseless on the ground."
Such theories are ingenious and suggestive, and may be true to a certain degree, but they hardly cover all the facts. It is possible that the Kallikantzaroi may have some connection with the departed; they certainly appear akin to the modern Greek and Slavonic vampire, "a corpse imbued with a kind of half-life," and with eyes gleaming like live coals. They are, however, even more closely related to the werewolf, a man who is supposed to change into a wolf and go about ravening. It is to be noted that "man-wolves" is the very name given to the Kallikantzaroi in southern Greece, and that the word Kallikantzaros itself has been conjecturally derived by Bernhard Schmidt from two Turkish words meaning "black" and "werewolf." The connection between Christmas and werewolves is not confined to Greece. According to a belief not yet extinct in the north and east of Germany, even where the real animals have long ago been extirpated, children born during the Twelve Nights become werewolves, while in Livonia and Poland that period is the special season for the werewolf's ravenings.
Those who wish to pursue further the study of the Kallikantzaroi should read the elaborate and fascinating, if not altogether convincing, theories of Mr. J. C. Lawson in his "Modern Greek Folklore and Ancient Greek Religion." He distinguishes two classes of Kallikantzaroi, one of which he identifies with ordinary werewolves, while the other is the type of hairy, clawed demons above described. He sets forth a most ingenious hypothesis connecting them with the Centaurs.
Excerpted from Christmas in Ritual and Tradition, Christian and Pagan, by Clement A. Miles, London: T. Fisher Unwin, 2nd Ed. 1913, pp. 229-247.