Gryla is very simalar to Krampus in many ways. While Santa brings good children presents, Gryla has an unsatisfiable hunger for naughty children and she is always grumpy. Like Krampus, she kidnaps them in a sack. She then brings them home to cook them alive and turn them into a stew.
Like Santa, Gryla has helpers. Her thriteen sons, known as the Yule Lads. They are usually much less cruel then their mother, and simply play pranks on people during the Christmas season (depends upon the version, some tales have the Yule Lads as homicidal child-eating monsters, especially older stories).
Gryla also has a giant cat named The Yule Cat. Whether or not you were naughty or nice, or if you're an adult or child, you are at risk of being eaten by The Yule Cat. The only people he won't eat are those who have gotten new clothes for Christmas.
Gryla is married to her third husband named Leppaluoi, who lives in the Dimmuborgir lava fields in a cave (this historic area is rife with supernatural mischief according to folklore, due to its unique natural "castle" formations and traditional tales of it being the place Satan himself landed when he fell from Heaven).