"Kallikantzaroi emerge from the depths of the Earth during the Dodekaimero, the 12 days spanning Christmas to the Epiphany, wreaking havoc. There are many remedies to keep them at bay: burning a pair of old shoes, placing colanders on one’s doorstep, or hanging a pig’s jaw over a home’s main door. But what ultimately drives these creatures back into the underworld is the Blessing of the Waters ceremony that occurs every year, and a kind of polar plunge that follows it."

https://www.atlasobscura.com/articles/christmas-goblins-greece