According to Greek folklore, these subterranean goblins come up to the surface once every year during the 12 days of Christmas. During the rest of the year they stay underground sawing away at the World Tree so that it will collapse and the Earth along with it. When they are just about to make their final cuts, however, Christmas comes around and they forget their original mission as they surface to terrorize humanity. After Christmas though, they return to their underground dwellings only to find that the tree has healed itself so they must begin their sinister work anew.