As per the book, The Yule Lads, Brian Pilkington states that due to the harshness of the winters and the poor and simple living conditions of the Icelanders, they were able to come up with some pretty awesome Folktales. Among those Folktales was the story of The Yule Lads and their parents. The Yule Lads, Grýla and Leppalúði are Trolls.
Grýla plays an important role in the Icelandic tradition as the mother of the Yule Lads. She is really ugly and mean and loves to eat stewed children. But she only wants rude, naughty or lazy children. It is said that if children are naughty, lazy or rude, Grýla will come find the children, put them in her sack that she carries on her back and take them up to the mountains. When she arrives back in the mountains she puts the children in her big black pot and makes Children Stew. I remember when I was a little girl my parents and grandparents would threaten me by telling me that if I was not good Grýla would come and eat me. I was scared of that ugly troll for years.
Look forward to reading about Leppalúði and the other romantic relationships Grýla had tomorrow.