Krampus, also known as the Christmas Devil and the Christmas Demon, is an accomplice of Saint Nicholas who appears in various legends most notably Austria and Hungary. He was used as a scare 'em straight figure that would be used by children's parents as a means to frightening them into obeying them lest they become the next victims of Krampus.
The most common depiction of the Krampus is that it resembles a Devil-like (similar to The Devil in Abrahamic religions), goat-like (similar to the mythical demon Baphomet), or satyr-like (possibly similar to Pan, the Greek god of wilderness and rustic music) with more fur in his body. As a colleague of Saint Nick, Krampus is essentially the anti-Santa Claus in that he brings suffering and torture to naughty children whereas Santa brings gifts. Most versions of the Krampus depicts the Krampus almost as a Knight Templar character who would severely beat children into obedience, or, in some versions, outright kills the child. Krampus may even go as far as to kidnap the child and put them into a sack and take them back to his lair to devour them. Or, he simply takes them to the underworld. One of his main discipline tools includes birch sticks that he could use to swat children with.
In Germany, there is a day called Krampushaeht, or Krampus Night, that would be celebrated on December 5, ironically on the same day as St. Nicholas Day. Nowadays, there are festivals thrown for the Krampus, and many people dress up like him.