In Greek folklore during the twelve days of Christmas, the goblin-like creatures said to cause mischief are the Kallikantzaroi.
The Kallikantzaroi are supernatural beings traditionally associated with the period from Christmas Day to the Feast of the Epiphany on January 6. Folklore describes them as emerging from underground during this interval to trouble people and damage household property.
One widespread story says that they spend most of the year trying to cut down the World Tree, only to find it restored when they return to the surface at Christmas. Their appearance and behavior vary between regional accounts, so they are not a single standardized character.
They are sometimes confused with ordinary Christmas elves or household spirits. Kallikantzaroi are specifically part of Greek and related southeastern European Christmas folklore, and their role is mischievous rather than gift-bringing.