The Yule Cat (Icelandic: Jólakötturinn or Jólaköttur) is a monster from Icelandic folklore, a huge and vicious cat said to lurk about the snowy countryside during Christmastime and eat people who have not received any new clothes to wear before Christmas Eve.  The Yule Cat has become associated with other figures from Icelandic folklore as the house pet of the giantess Grýla and her sons, the Yule Lads. 
The threat of being eaten by the Yule Cat was used by farmers as an incentive for their workers to finish processing the autumn wool before Christmas. The ones who took part in the work would be rewarded with new clothes, but otherwise get nothing and thus be preyed upon by the monstrous cat. The cat has alternatively been interpreted as merely eating away the food of ones without new clothes during Christmas feasts.  The perception of the Yule Cat as a man-eating beast was partly popularized by the poet Jóhannes úr Kötlum in his poem Jólakötturinn. 
As if coal in the stocking wasn’t bad enough.