The kresnik is a kind of vampire fighter found in Istria in Croatia and Slovenia, the bitter enemy of the kudlak, the local vampire.
This lore was found among Croatians and some Slovenians in the north Adriatic peninsula of Istria and islands off its coast.
The root of the word is krat, meaning a cross, implying that the kresnik was aided by the forces of light, and was a local representative of good.
Similar to the dhampir, the kresnik was the result of the folkloric development of the shaman, someone who fulfilled the role of protector of the inhabitants and their homes.
Every town or community had a kresnik, just as it had its own kudlak (an evil wizard or a vampire). Where the kresnik was the representative of goodness and light, the kudlak symbolized evil and darkness. The two were always embroiled in titanic struggles in which the adversaries changed into animal shapes, pigs, oxen, and horses.
Good was recognizable by its white color, although the fighters could transform into a dramatic wheel of fire. Invariably, the kresnick defeated the kudlak, as the foes of God could never hope to overcome the true agent of light.
A person born with a caul could either become a kresnik or a kudlak. It was sometimes said that a clear or white caul indicated the child would become a kresnik but a red or dark caul meant he'd become a kudlak. When in doubt, the midwife sometimes ran to the window and shouted several times: "A kresnik is born! A kresnik!" to magically insures its fate for the better.
Ginzburg says that in Istria the midwives sewed the caul around the infant kresniks, under their armpits; and that on the island of Krk the caul was dried and mixed with food for the infant to eat. (In Romania and Poland there were similar measures to prevent a person born with a caul to become a "vampire".) The kresnik became an active nocturnal battler often at age seven, but sometimes later - at eighteen or twenty-one. It seems likely that the young kresniks went through a process of initiation and training given by the elder kresniks to acquire their abilities.
Variations on these warriors were found in Slavic lands. In Hungary, the kresnik was called talbos, with the main purpose of defending vital crops.In “Ecstasies”, Ginzburg also mentions: in North central Croatia - the mogut - the son of a woman who died after giving him birth or who had an unusually long pregnancy; in Southern Dalmatia (a part of Croatia between Bosnia-Herzogovina and the Adriatic Sea) - the negromanat - born with a tail.; in Montenegro and parts of Bosnia-Herzogovina - the zduhac - also born with a caul.