A strange Austrian celebration at 5th December (just before St. Nick's day, at 6th December) dealing with demons and such things. A day to scare the children and put your demon mask on – a good excuse to drunk for real or to expelling evil Spirits:
There are more images at Monster Brains blog and a interesting article here (a curious note: Santa Claus as a Christian avatar of Thor).
There's a very good horror short movie that came out last year about that whole "running around dressed as Krampus" thing, called Raunacht. If you speak German, I recommend it highly; no gore, very spooky.