The Greek Kallikantzaroi appear during the Twelve Days of Chrsitmas. In Greek folk tradition it is believed that when Christ is born, so too are these winter spirits. They are half-animal, half-human monsters, black, hairy, with huge heads, red eyes, goats’ or asses’ ears, lolling red tongues, ferocious tusks, long curved claws and animals’ feet. Though they normally live in the underworld, at this time they attempt to climb up the World Tree to emerge on earth. In the Macedonian plain of Saraghiol, the Kallikantzaroi emerge from a stone named Kiatra Schuligan, beneath which an abyss opens, black and deep, and the sound of laughter, sobs and screams can be heard issuing from it, along with the sounds of pipes and beating drums. 
The Kallikantzaroi hide in dark places during the day, but come out at night, led by the Great Kallikantzaros riding a cock. They lurk around lakes and crossroads in particular. People who meet them are challenged with the riddle “hemp or lead?” and if they answer “lead” they are attacked and half torn apart.
The Kallikantzaroi enter houses by swarming down the chimneys to smash the place up and eat all the Christmas pork, urinate on all the water and wine and whatever food which remains, leaving the occupants half dead with fright or violence. They will disappear at the third cock crow each morning when the light of the sun sends them back to their dark holes.
To scare them away, the Greeks kept their Christmas log burning. They also burned old shoes, believing the smell would repel the creatures. Houses had to be protected from these onslaughts by marking the front door with a black cross on Christmas Eve (though even then, the demons can trick householders into opening it by imitating the voice of a family member), the burning of incense and the invocation of the Trinity, the lighting of the Yule log, the burning of something that smells strong, and the hanging of pork-bones, sweetmeats, or sausages in the chimney.
The signal for their final departure does not come until Twelfth Night with the Kalanda festival, when the ‘Blessing of the Waters’ ceremony takes place. Some of the holy 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 to which the Winter Spirits react:
“Quick, begone! we must begone,
Here comes the pot-bellied priest,
With his censer in his hand
And his sprinkling-vessel too;
He has purified the streams
And he has polluted us.”
Like other such creatures elsewhere, they are often said to be spirits of the dead. Children born at Christmas are susceptible to becoming Kallikantzaroi, as are people with inept guardian angels. In some places they are thought to be transformed humans placed under a spell after being born with a caul during the Twelve Nights
© Anna Franklin, Yule, Lear Books, 2010
 This Macedonian lore of the kallikantzaroi connects high rock formations with the dead, especially infants who died without baptism. Similar associations were made by the Scots, who used to have a custom of burying unbaptised babies among inaccessible rocks. The child’s spirit entered into the rocks and became the echo (called ‘child of the rock’ in Gaelic).
 Christmas in Ritual and Tradition, Christian and Pagan, by Clement A. Miles, London: T. Fisher Unwin