Stekkjarstaur - Icelandic Yule Lads (December 12th)

Here in Iceland we have 13 of so-called Yuletide lads. They come into town one by one, the first on the night between December 11 and 12 and the last arriving on Christmas Eve. Then they'll return to their home in the mountains one-by-one again.

In latter years they've taken on Santa's role to give kids gifts. Every kid in Iceland will put a shoe in the window and the 13 nights before Yule the Yule-lad of the day will put something in there. But originally they were pranksters and thieves. Mostly they stole food and their names generally reflected on their favorite food.
The Yule Lads are traditionally said to be the sons of the mountain-dwelling trolls Grýla and Leppalúði. They would trek from the mountains to scare Icelandic children who misbehaved before Christmas. Additionally, the Yule Lads are often depicted with the Yule Cat, a beast that, according to folklore, eats children who don't receive new clothes for Christmas.

Every night, one Yuletide lad visits each child, leaving gifts or rotting potatoes, depending on the child’s behavior throughout the year.

Stekkjarstaur 
December 12th

He is particularly fond of sheep's milk but has enormous trouble with getting it because his stiff knees make impossible to bend his legs.

Often mistakenly believed to have wooden peg-legs, but he's described to have 'staurfætur' which is commonly used for peg-legs. It does however just mean a leg that can't bend the knee. It wasn't an uncommon ailment in former days and is more likely that he had stiff legs than actual wooden legs...
Icelandic 

Stekkjarstaur kom fyrstur,
stinnur eins og tré.
Hann laumaðist í fjárhúsin
og lék á bóndans fé.

Hann vildi sjúga ærnar,
þá varð þeim ekki um sel,
því greyið hafði staurfætur,
- það gekk nú ekki vel.

English

Gimpy was the first,
Stiff like a tree.
He snuck into the stables,
And fooled the farmer's sheep.

He wanted to suck milk from them,
- They did not care for that,
And because he had peg-legs
- It did not go too well.

Stekkjarstaur harbours a stiff temperament, is stiff temperament, is stiffly set in his ways and very conservative. Some claim he secretly practices yoga, but this has never been confirmed.

He's the tallest of the brothers. That cross of troll, elf and human ancestry gave him a very long and rather stiff pair of legs. Legend says he walks as though they were made of wood, and he has to use a long walking stick to be able to walk properly. Some folk art portrays him as having two wooden prosthetic limbs, but I go more for him just having long, straight legs. They do help him take enormous strides, so he can travel further than anyone else in his family.

His specialty is in terrifying sheep and, on occasion, stealing them. So, starting on this evening and running through Christmas, Vikings make sure their sheep are well locked away or the next morning they might have some very terrified sheep ... or, even missing sheep.

Berglind, Iceland24

Stekkjarstaur - Icelandic Yule Lads (December 12th)