The story of the Icelandic Yule Lads

Now 12th December has arrived and the day has come to tell you about the 13 Yule Lads, my favourite Icelandic christmas story (a bit rough and wild).

While in many countries Father Christmas, the Christ child or Santa Clause arrive on 24th or 25th December with loads of christmas presents, the story goes a bit different in Iceland. Between 12th and 24th December thirteen half trolls come down the highlands and plague the farms. They try to steal food and goods and cause trouble. Every day one of them arrives until all of them will have come by Christmas Eve. Then, every day one by one they will leave until the last one will be gone on 6th January.
Their mother is the troll woman Grýla living in the mountains being a dread to the Icelandic children which she loves to eat. Her companion animal is the so-called Christmas Cat which will abduct and eat all children which haven't gotten any clothes on Christmas. The Yule Lads' dad is called Leppalúði, and he is basically a lazy guy who doesn't have much to do with the terror regime of Grýla.
It is said that the Yule Lads bring rotten potatoes to misbehaving children which they put into their shoes. These days, they have become a bit more friendly towards humans and bring little presents to the children. Children put their shoes into a window and during the nights when the Yule Lads arrive they will place a little present into them.

Troll woman Grýla chasing children.

Here is the saga of the Yule Lads (freely translated from the little book "Jólin koma"):

I want to tell you the story
of the Yule Lads,
which came down the hills to scare
us on our farms at home.

They were seen up in the mountains
- as many know -
in a long row
on their way down into the country.

Grýla was their mother
and gave them troll milk,
their father was Leppalúði
- they were bad creatures.

They were called the Yule Lads
- on christmas they appeared.
And they came one by one,
but never two at once.

They were thirteen,
Those gentlemen,
Who didn't want to make trouble
All at once.

To the doors they sneaked
And pulled the latches out.
And they were eager to search their way
Into the kitchen and pantry.

Sneaky on their faces
They hid here and there,
To do mischieve
When nobody was close.

And like this, though somebody saw them,
They did not hesitate
to frighten people - and disturb
their home peace.

Today, on 12th December, the first of them, Stekkjarstaur, arrived, and this describes what he is up to:

Stekkjarstaur came first
Rigid like a tree 
He sneaked into the sheepfold
and played with the farmer's sheep.

He wanted to suck the ewe's milk,
This was difficult for him,
Because the poor thing had feet stiff like wood
Stealing the milk didn't go well.

Stekkjastaur up to no good.