In Iceland, naughty children don't just get lumps of coal during the Christmas season. Sometimes, they get eaten. Meet Grýla, the fearsome fairy tale ogre that keeps Icelandic kids toeing the line during the holidays.

The Christmas Witch, as some English-language sources call her (like Smithsonian magazine, which took a fun dive into the myth in 2017) is actually more like the Christmas Troll, one of many scary, man-eating trolls featured in Icelandic folk tales. During jól, Iceland's Christmas season, she supposedly comes down from her cave in the mountains to gather up ill-behaved kids for her and her lazy and browbeaten husband Leppalúði to make into stew.

Folk tales and poems about Grýla have been around since at least the Middle Ages, according to British folklore researcher Jacqueline Simpson's 1972 book Icelandic Folktales and Legends. In Icelandic folklore, trolls are stupid giants, most of whom are very dangerous and actively hate Christianity. They're usually used to explain rock formations, which many legends claim are either trolls turned to stone or stones thrown by a troll at a church. In the 13th century, the word grýla was a general term for a she-troll, but eventually, it came to name a specific, child-eating monster.

The legends don't agree on what, exactly, Grýla might look like, though like all Icelandic trolls, she's a gross, massive giant. One rhyme says she has 15 tails, each of which holds 100 bags with 20 children in each bag, doomed to be a feast for the troll's family. Another says she has 40 tails, and still another says she carries a bag of children on her thigh. Some poems say she has 300 heads, each of which has three eyes. Others describe eyes in the back of her head, ears that hang so long that they hit her in the nose, a matted beard, blackened teeth, and hooves. All these stories agree on one point: She's very, very ugly.

Grýla isn't a standalone figure in Icelandic folklore, though. She is the mother of the Yule Lads, 13 mischief makers that supposedly visit on the 13 days of Christmas. Her companion, the Jólakötturinn—the Yule Cat—is said to have a taste for human flesh himself, lurking in the snowy countryside and gobbling up anyone, adults or children, who didn't get any clothes for Christmas—a sign that they didn't work hard enough.

Grýla functions as a cautionary tale, but most adults don't really believe in her, unlike, say, elves, which a number of modern Icelanders consider an important and very real part of their culture. As Simpson writes in the introduction to her book, even hundreds of years ago, "parents taught their children to fear the bugbear Grýla, but did not believe in her themselves."

Some tales have softened Grýla's image over the years. In an episode of Netflix's The Chilling Adventures of Sabrina, for instance, she's presented as a powerful witch who protects mistreated children, not a monster who's intent on devouring them. She's now depicted in statues and Christmas installations all over Iceland—even at airports—but in many cases, she retains at least a little of her scary vibe.

Love Yuletide monsters? Take our quiz to find out which legendary Christmas figure you're most like.