In Icelandic tradition, the Yule lads are thirteen trolls who arrive one at a time on each of the 13 days before Christmas and depart in the order they arrived, on the days after Christmas Day. On Christmas Eve, the troll witch Gryla leaves the mountains to seek any children who had been ill-behaved or were without the protection of their parents, taking them back to the mountains where she cooks them into a stew for her lazy husband.
The thirteen Icelandic Yule Lads are described with the acts they are infamously known for tormenting human communities. More can be found at the Smithsonian Magazine here
Sheep-Cote Clod: He tries to suckle yews in farmer’s sheep sheds
Gully Gawk: He steals foam from buckets of cow milk
Stubby: He’s short and steals food from frying pans
Spoon Licker: He licks spoons
Pot Scraper: He steals unwashed pots and licks them clean
Bowl Licker: He steals bowls of food from under the bed (back in the old days, Icelanders used to sometimes store bowls of food there – convenient for midnight snacking?)
Door Slammer: He stomps around and slams doors, keeping everyone awake
Skyr Gobbler: He eats up all the Icelandic yogurt (skyr)
Sausage Swiper: He loves stolen sausages
Window Peeper: He likes to creep outside windows and sometimes steal the stuff he sees inside
Door Sniffer: He has a huge nose and an insatiable appetite for stolen baked goods
Meat Hook: He snatches up any meat left out, especially smoked lamb Candle Beggar: He steals candles, which used to be sought-after items in Iceland
Since 1746, the Yule trolls became less scary and presented as more mischievous, trickster characters who were depicted as jolly Santa Claus-like figures who left gifts for the well-behaved children and potatoes for the ill-behaved ones. The Yule trolls as they had been described in early traditions and folktales described them as emaciated and clothed in rags. There is a current movement in Iceland to return the Yule Lads to their original descriptions and depictions as the vagabond and desperate orphans accompanying Gryla.