In Iceland they say that 13 lads herald the arrival of Yule. From December 12 to Christmas Day (yes - they've christianised the tradition but still call them Yule lads) a new rascal arrives each day. They are the sons of the troll Gryla and friends of the hungry Yule cat.
The first to arrive is Stekkjastaur, the sheep worrier, and the rest of his brothers are just as naughty: for example there's the sausage stealer, window peeper, door slammer and lots of other wickedness. After Christmas Day they leave, one by one, until Twelfth Night, when Icelanders celebrate the end of the holiday season with bonfires and a party.
The Yule Cat, throughout the season, will eat anyone who does not have a new item of clothing to wear. And you'll have to wait for an explanation of why.