The Yule Cat is the monstrous cat of Grýla and Leppalúði. It helps them frighten, kidnapp and devour naughty children at Christmas
Myth
The Icelanders refer to it as að fara í Jólaköttinn, literally to end up in the Yule Cat, the common interpretation being that the Yule Cat will eat those who do not receive any new clothing at Christmas. Yet some people favour a slightly more benign interpretation: that the Yule Cat will eat the food of anyone who does not receive a new item of clothing for Christmas.
Even to this day, many people consider receiving new clothing for Christmas to be of extreme importance. It is common for people to dress in new clothing from head to toe on Christmas Eve. Some sources suggest that female farm workers in the old days worked extremely hard to produce one item of clothing after another during Advent, all in an effort to save the farm folk from the claws of the Yule Cat.