Der Speigel has an article on Krampus:

In Austria, Santa keeps track of who's been naughty and nice -- and unleases a 7-foot-tall horned devil on the naughty. He's called the Krampus, and he's unlike any Christmas tradition you've ever seen.

Santa's all well and good, but darker things have always lurked in Austria's woods. Take the Krampus, a towering, hairy creature with a long, long tongue, goat's head and horns and cloven feet. Krampus is no dancing Greek satyr. Instead, he roams rural Austria clad in chains and carrying a stick, terrifying misbehaving children on Dec. 5, the night before St. Nicholas' Day.

Depending on who you believe, Krampus is very old indeed. Some say the tradition stems back to the pre-Christian era, and that the Krampus known and feared by Austrians today is a version of an ancient god incorporated into Christian holidays.