The idea behind Čarodějnice goes back to pagan times. April 30 was allegedly when witches would gather on high mountains. The fires were built on hills to ward off the evil, as the smoke drives the witches away. In Germany, the event is called Walpurgisnacht, which refers to the eve of the feast of St Walpurga, who can be called on the fight infestations, rabies and witches.