On the eve of 5th December, you will meet a strange trio - Mikuláš (Nicholas), Anděl (the Angel) and Čert (the Devil).
All three characters walk the streets, stopping children and asking them if they were good in the past year. Children are often terrified of the the Čert because bad kids would be put into his sack and taken to hell. After singing a song or reciting poem to the trio, they are rewarded with sweets handed out by the Angel.
Adults or teenagers who dress up to bring joy to the children are rewarded too - whether with the money or with shots of alcohol. December nights are very cold after all, which in some cases unfortunately leads to rather tipsy unearthly beings.
My Canadian friend nicely summarized this event as “it’s kind of like Halloween, only with adults dressing up”. While Czech and Slovak Mikuláš is pretty much the same, in Austria, Bavaria, Croatia and Hungary they have instead of Čert terrifying Krampus.