Additional Information:  Figures among the Kongo fall generally into a number of identifiable categories whose interpretation can vary and cross over as to function and meaning. Among the various Kongo groups sculpted figures represent elites and royals with a large number serving as power figures that would have magical materials attached. Sometimes, they would be covered with the familiar metal objects beaten into their surfaces which led to their being identified as ‘nail fetishes’. These figures known as nkisi serve magical ends control and direct ambivalent spirits.  Other Kongo figures serve to represent ancestors or will function as shrine objects where offerings and prayers are offered to the spirits.

 In fact the practitioner, priest or diviner known as an nganga would fill the cavity in the belly with magical substances and would cover them with a mirror. Sometimes, pieces of glass are also encrusted in the eyes. These mirrors have the same meaning than the white pigment around the eyes. Their role is to accentuate the sense of mystery surrounded this kind of Nkisi and to confirm its ability to see the future, as the nganga use the white pigment , as well as  the mirror as a device and a metaphor for the power of "being able to read the invisible". 

Recommended Reading: J. Cornet; Art of Africa, Treasures from the Congo. 1971. E. M. Maurer and Niangi, B.: Spirits Embodied: Art of the Congo. 1999.Art of the Congo, Walker Art Center.