In Yaka terminology, Mbwoolo-Tchio images aiebiteki, figures used to support or contain special concoctions. Without these applied preparations, which permeate the surface or, more rarely, are inserted into a small ventral cavity, they are without meaning to the Yaka and merely await employment by a ritual specialist. But when charged with these ingredients, they become n’kisi,-“medicines-poisons” that “make-ill” (kukwatn) through an invisible influence, or “make-well” (kubuka) by removing this influence. Owned by specific lineages rather than individuals, the Mbwoolo pass from one generation to another through the “seizure” and subsequent cure of a man or woman who by this ordeal is entitled to become its ritual officer, the nganga. Originally, Mbwoolo enters a lineage through the theft of some object placed under the n’kisi’s protection and becomes a hereditary “sickness” destined to reappear in future members. Its curative capacity can be induced only by the one who first invoked Mbwoolo or by a special ritual practitioner qualified to activate it. Thus Mbwoolo functions as both the calling and temporary abeyance of a curse. But once it has entered a lineage, Mbwoolo offers some benefits. This “medicine-poison” serves the lineage by protecting property and assures the well-being of future generations. Moreover, lineage
solidarity is furthered in Mbwoolo ritual, and its nganga, or official practitioner, is assured a lucrative income.”