The night before December 6 is known as Krampusnacht, or Krampus Night.
The Feast of St. Nicholas is celebrated in parts of Europe on 6 December. In Alpine countries, Saint Nicholas has a devilish companion named Krampus On the preceding evening, Krampus Night or Krampusnacht, the hairy devil appears on the streets. Sometimes accompanying St Nicholas and sometimes on his own, Krampus visits homes and businesses. The Saint usually appears in the Eastern Rite vestments of a bishop, and he carries a ceremonial staff. Unlike North American versions of Santa Claus, in these celebrations Saint Nicholas concerns himself only with the good children, while Krampus is responsible for the bad. Nicholas dispenses gifts, while Krampus supplies coal and the ruten bundles. — wikipedia
Krampus, whose name is derived from the German word krampen, meaning claw, is said to be the son of Hel in Norse mythology. The legendary beast also shares characteristics with other scary, demonic creatures in Greek mythology, including satyrs and fauns. The legend is part of a centuries-old Christmas tradition in Germany, where Christmas celebrations begin in early December.
Krampus was created as a counterpart to kindly St. Nicholas, who rewarded children with sweets. Krampus, in contrast, would swat “wicked” children and take them away to his lair (or leave them a lump of coal).