The kallikantzaroi are evil goblins, found in Greek folklore, who live underground and saw the World Tree to try to collapse the earth. When Christmas season begins, they abandon their task to terrorize humans. On Epiphany, they return but the tree has healed itself.
Man being persecuted by goblins and other spirits. From “Le serpent de la Genèse” (The Serpent of Genesis) Volume 1, by Stanislas de Guaita, 1920. Source: Embassy of the Free Mind