This work looks at the figure of the Southern Great Chaco guaycuros mentioned in the jesuit sources of the xviii century. The twofold aim is to bring these jack groups closer to the chamanic system and to discuss the concepts of chamanism and brushery in these societies. To this end, the works of Martín Dobrizhoffer, Florián Paucke, José Sánchez Labrador and José Jolís are analysed.