Many countries have some sort of folk creature that comes out to hurt or kill naughty children. The origins are unclear, but all stem from the concept that parents wanted their children to behave and to stay inside (where it's safe) from the brutal elements. So parents threatened them with creatures that would kill them. Most of these creatures are still recognized today, although they all seem to only show up around the winter solstice.
According to Icelandic folklore, December 12th starts the first day that the first of thirteen Yule Lads come to visit. Each stay for thirteen days. All have names that correspond to the offerings that they seek, or gifts that they leave. Tradition is for children to leave a shoe on the windowsill so that gifts (or rotting potatoes for the bad children) may be left. Depending on who is discussing (and what century is referenced) the lads, their demeanor is anywhere from being harmful pranksters to nefarious trolls. Throughout the years, the number and names of the lads have changed as well.
Stekkjarstaur is the first to arrive,on the 12th. His name means Sheep-Cote Clod, and is a menace to sheep. however, this is a bit difficult for him, since both of his legs are pegs.
Giljagaur shows up next on the 13th. Gully Gawk hides in gullies and tries to steal the cow's milk. .
Stúfur (Stubby) is noticeably short, and shows up on the 14th. Pans that are left out unwashed are stolen by him so he can eat the crusty leftovers.
December 15th marks the arrival of Þvörusleikir, the Spoon-licker, steals spoons. He is identified by being emaciated.
The 16th of December welcomes in Pottaskefill, the Pot-scraper, is similar to Stubby. However, Pottaskefill only steals the leftovers in the pots, and not the pots themselves.
The next one to show up on the 17th is Askasleikir, the Bowl-licker. He hides under tables and beds waiting for people to put down their bowls, which he steals to eat the leftovers.
Hurðaskellir is the Door-slammer. Can you guess what starts happening on the 18th? Do not
blame the draft for all of the doors slamming! He also prefers to stomp around a bunch, so be prepared for a loud time.
Skyrgámur is Skyr-gobbler. Skyr is similar to yogurt, which this guy prefers to eat.
Bjúgnakrækir is the sausage-swiper. Back when people would smoke their own sausages, this guy would hide in the rafters and grab them up to eat starting on the 20th.
Gluggagægir, the Window-peeper, is nothing more than a Peeping Tom. He looks through the windows and tries to find things to steal.
Gáttaþefur is a weird one, the Doorway-sniffer. He is easily identified by his large nose, which he uses to sniff out bread and other baked goods to eat.
Ketkrókur is the simple Meat Hook, who uses a hooked instrument to steal meat to eat. He prefers lamb above all other meats.
Kertasníkir, the Candle-Stealer, steals not just candles, but tallow and lard used to make candles.
In addition to the thirteen lads, there is the mother of the lads, Gryla. She is an ogress who searches for her children, the lads. Any naughty children that she comes across while searching for her own children, she boils in her cauldron to make her favorite stew.
If that wasn't bad enough, there is also the Yule Cat that lives with Gryla and the lads. Sounds charming in English, but the name of this black cat is Jólakötturinn, and he only ate once a year. He is considered a monster that prowls Iceland to kill anyone who does not receive new clothes during Yule. I now know why my mother and grandmother always gave me socks for Christmas.
My point is this - be good. If you can't be good, stay inside for the next few nights. Have a glad Yule!