A rough, cracked surface obscures exact identification of the organic and inorganic materials assembled to create the boli (pl.: boliw), or power object, shown here. Such objects play an essential role within Bamana spiritual life. Boliw have attracted much attention from Western observers due to their amorphous forms and unusual materials. The bulbous and amorphous shape is rather idiosyncratic within the repertoire of Bamana art. Boliw are composed of a wooden armature "core" wrapped in white cotton cloth, around which clay and sacrificial materials are encrusted. This boli has four short "legs" upon which it sits, as well as a single hump rising from the top. The creature that a boli represents is unidentifiable, but many take on the loose zoomorphic form suggested by this work, while others may be anthropomorphic.

The primary function of a boli is to accumulate and control the naturally occurring life force called nyama for the spiritual benefit of the community. The composition of the encrusted patina varies, but all the ingredients possess this inherent and important spiritual energy. The encrustation may include the blood of chickens or goats, chewed and expectorated kola nuts, alcoholic beverages, honey, metal, animal bones, vegetable matter, and sometimes millet. Sometimes this added matter is so extensive that it obscures the original wooden form and takes on a shape all its own. As the encrustation cracks and hardens throughout the years, it gives the impression that these ingredients are tightly packed within the boli. As the sacrificial materials accumulate over time, each added layer affords the structure greater spiritual power.

Boliw and their numerous ingredients have been interpreted in a number of different ways. It has been suggested that the disparate elements of which boliw are composed symbolize the various parts of the universe, so that the whole can be read as a model of Bamana cosmological belief. Such power objects are owned by male associations whose members progress through induction processes that span decades. Over time, they attain an esoteric knowledge of the natural and spiritual world. Opaque and mysterious to the uninitiated eye, boliw are safely handled only by those association members equipped with the most rarified expertise and knowledge.