Ever since Christoph Waltz (the gem of Austria) did an entertaining and extremely funny interview with Jimmy Fallon (seen here), and now that a Krampus movie is about to hit theaters in the States (and elsewhere), a lot of friends and family have some questions about this mythical figure. My first year in Austria, I asked people about Krampus after I started seeing hilarious (in a dark-humor sort of way) chocolates and various other sweets with a "devil" on them. Instead of learning the backstory about this dark figure I learned that it is common for young men to dress like Krampus and beat people on a scale from bruises\welts to brain damage. Since people are not fond of themselves or loved ones becoming irrevocably brain damaged due to intoxicated and anonymous individuals playing dress-up, in most villages people have to register so that they can be reported for too much violence. There are, however, still some smaller villages that have a more "it's traditional to maybe die or become permanently maimed" attitude towards the whole affair so maybe you should ask some locals before strolling around after dark on 12/5.
Here are some real Krampus customes from a town in Tirol. (picture from www.meinbezirk.at)
From what I have gathered about Krampus, he is simply the dark-side to Santa's kindness. Good children get toys, bad children get beaten with a chain/whip and possibly taken away from their homes forever. Very ying and yang and also terrifying. Here is the wiki about him if you are still curious. In recent years Krampus has become much less traditional according to locals that grew up with him, but for a foreigner it certainly highlights some of the differences in our cultures. On a side note, the lyrics to "Santa Claus is Coming to Town" take on a sinister tone once you realize Santa Claus'll be bringing his dark buddy with him.