From Wikipedia:
The benandanti (“Good Walkers”) were members of an agrarian visionary tradition in the Friuli district of Northeastern Italy during the 16th and 17th centuries. The benandanti claimed to travel out of their bodies while asleep to struggle against malevolent witches (streghe) in order to ensure good crops for the season to come. Between 1575 and 1675, in the midst of the Early Modern witch trials, a number of benandanti were accused of being heretics or witches under the Roman Inquisition.
According to Early Modern records, benandanti were believed to have been born with a caul on their head, which gave them the ability to take part in nocturnal visionary traditions that occurred on specific Thursdays during the year. During these visions, it was believed that their spirits rode upon various animals into the sky and off to places in the countryside. Here they would take part in various games and other activities with other benandanti, and battle malevolent witches who threatened both their crops and their communities using sticks of sorghum. When not taking part in these visionary journeys, benandanti were also believed to have magical powers that could be used for healing.
Across Europe, popular culture viewed magical abilities as either innate or learned; in Friulian folk custom, the benandanti were seen as having innate powers marked out at birth.[2] Specifically, it was a widely held belief that those who in later life became benandanti were born with a caul, or amniotic sac, wrapped around their heads.[3][4] In the folklore of Friuli at the time, cauls were imbued with magical properties, being associated with the ability to protect soldiers from harm, to cause an enemy to withdraw, and to help lawyers win their legal cases.[5] In subsequent centuries, a related folkloric tradition found across much of Italy held to the belief that witches had been born with a caul.[5]
From surviving records, it is apparent that members of the benandanti first learned about its traditions during infancy, usually from their mothers.[6] For this reason, historian Norman Cohn asserted that the benandanti tradition highlights how “not only the waking thoughts but the trance experiences of individuals can be deeply conditioned by the generally accepted beliefs of the society in which they live.”[7]