Belznickel lore:

A scary, darker Christmas visitor in the South West of Germany and amongst German-speaking communities in the United States was Belznickel. Also known as Belschnickel, Belznickle, Belznickel, Pelznikel, Pelznickel, the name translates as "Walloping Nicky," i.e., he is a Nicholas that thumps! Because of this, some say he is a version of St Nicholas, but he isn't exactly. While Nicholas is the name of the saint, there are also examples of the name Nicholas being used for the devil.

Belznickel is crotchety, grumpy, and very scary, particularly for bad children. At his most fearsome, he would appear at the door, dressed in ragged furs with a long white beard, rattling chains, and branches of a birch against the window until let in. Once he entered the house, he would enter the house and would be able to sense which children had been bad. Bad children would be hit with a switch (in some versions, sometimes it would just be a threat!) and made to perform a song or dance and promise to be good. Belznickel would reward the children with gifts of candies, fruit, and cookies.

Thus Belnickel could serve the role of both Santa Claus and Black Peter at the same time. He sometimes comes on St Nicholas's Day, but in others, he comes a few weeks before the Christkind on Christmas Eve.

Other Similar Bogeymen

There are many other bogeymen across Europe, including Knecht Ruprecht (Servant Ruprecht), Hans Trapp, Beelzebub (based on a name for a demon), and Père Fouettard (whipping father in France). They all act in a similar manner.

Belznickel comic lore:

Not much is known about this evil version of Santa, only that he's far more violent and gruesome than the legends portray him as.

While he may look exactly like how Santa is often portrayed as, this isn't what he really looks like and some who have survived an encounter with him say his true form is far too horrifying to describe.

Belznickel has grown to enjoy the taste of cookies, preferably with chocolate chips and M&M's, but instead with milk he prefers them with blood of his victims.

Here's the original piece of Belznickel aka evil Santa.