They are a part of old folk tales and they are not really well behaved. The best part for Icelandic kids is the fact that these 13 santas come to town one by one starting on the 12th of December and the last one on the morning of the 24th, which is the day icelanders celebrate as Christmas, go to church and open presents. These santas bring each kid a small gift, but since it takes a long time they use the night to do it and the kids have to be a sleeo otherwise they don't get a gift. The perhaps the strangest part of this tradition is that to recieve a gift kids have to put a shoe in their window for the santa of the night can put the gift in.
When I was young I rember making paper shoes with cotton ball on the toe :)
Today Margret and I made this kind of a shoe for her to put in her window. I didn't have a model or pattern to follow so I just made it up. This is the result. Now we just have to wait for the santas :)