What are kallikantzaroi and how do you get rid of them?

Christmas trees are not commonly used in Greece. In almost every home the main symbol of the season is a shallow wooden bowl with a piece of wire is suspended across the rim; from that hangs a sprig of basil wrapped around a wooden cross. A small amount of water is kept in the bowl to keep the basil alive and fresh. Once a day, a family member, usually the mother, dips the cross and basil into some holy water and uses it to sprinkle water in each room of the house. This ritual is believed to keep the Killantzaroi (Kallikantzaroi or Karkantzaroi) away from the house.

When a house is not prepared against their coming, "by chimney and door alike they swarm in, and make havoc of the home; in sheer wanton mischief they overturn and break all the furniture, devour the Christmas pork, befoul all the water and wine and food which remains, and leave the occupants half dead with fright or violence."

Both above paragraphs from the following website...

http://www.sfakia-crete.com/sfakia-crete/christmas.html