NIKOLAUS was a Bishop who gave fruit, nuts and sweets to children on the eve of 6th of Dec.
He would ask whether the children had been good, whether they had been nice to their siblings, tidied their rooms and did all their homework. He has a golden book from which he can read their misdeeds and good deeds.
The children might perform a song or poem for him, to convince him they could behave well.
Nikolaus may bring Knecht Ruprecht, also called Krampus, he is a dirty fellow who will put a child that has been very bad in his sack and take them away.
However, be happy when Nikolaus comes to your door, he brings gifts and will give you his blessing.
(not under any circumstances for children!)