The callicantzaros was a peculiar type of Greek vampire that was discussed by Leo Allatius in his 1645 treatise, De Graecorum hodie quorundam opinationibus. The callicantzaros was related to the sanctity ascribed to Christian holy days at Christmas time. It was said that children born during the week between Christmas and New Years (or Epiphany of Twelfth Night- the evening when the Three Wise Men are supposed to have arrived at Bethlehem to present their gifts to the baby Jesus) are considered unlucky. These children were described as feast-blasted and believed to be destined to become vampires after death.
The callicantzaros was distinct among vampires in that its activities were limited to the 12 days between Christmas and Epiphany. During the rest of the year, it traveled in some vague netherworld.
It was distinguished by its manic behavior and extended fingernails. The callicantzaros would seize people with its talons and tear them to pieces. Reports of the callicantzaros’ appearance vary, which is possibly related to the state of maturity of the person deemed to be a future vampire.
The callicantzaros effect on everyday life was definitely noticeable, especially for the parents of children born within the 12 day period. These children were treated with some degree of hostility. The parents would fear that the children would act out vampiric fantasies as they grew up and would harm any siblings.
It is said that the first victims of a callicantzaros whose parents were mortal were often its own siblings, who he was apt to bite and devour. In order to prevent an infant who was born within the 12 days from becoming a callicantzaros, they were sometimes held feet down over a fire by one of the parents until the toenails were singed.