Yes, this is another Czech Advent tradition that involves scaring children! St. Ambrose used to chase children on December 7.

St. Ambrose (sv. Ambrož in Czech) was a bishop from Milan and his symbols are a beehive and a twig whisk. You can see both at the peculiar tradition performed at the Day of St. Ambrose which is December 7 which is currently being revived in some places. Dressed in white, with a black pointy hat and a white veil covering his face, a man or a boy representing the saint would come to the local church at sundown and chase children around it. Just like Barborky, Mikuláš and Lucky, this is another tradition that involves scaring children.
The children would gather in a group and shout at St. Ambrose in great expectation. They know there is more than just fun in for them. St. Ambrose is carrying candy. He throws it around for the children to collect but as they do, they become and easy prey to St. Ambrose’s whisk (a broom with white paper glued onto it).

Why is this tradition not more wide-spread? Unlike other traditions that are dying out, this one was never well-known all around Bohemia, Moravia and Silesia because it was observed only in places with a church dedicated to St. Ambrose. The regions I found mentioned in literature are the following: surrounding of the town Kolín, Suchdol (unknown whether in Prague or Suchdol nad Odrou), Souš (Čouš) in Most and Nové Dvory.

The Day of St. Ambrose usually brings a very cold weather after the Andrew-Nicolas warming and so the weather saying goes like this:
| „O sv. Ambrožu ucpi v sednici každou díru.” | “On St. Ambrose Day, plug all holes in the room.” |