Among the various Kongo peoples, nkisi means a sacred medicine. This word has been extended to include objects containing that medicine as well. The carved wooden statues referred to in the 19th century as nail fetishes and more recently as power figures containing medicine that imbues them with divine power, are therefore nkisi as well. Due to the medicine they contain (which is administered by a witch doctor or nganga), they act as agents of divine power, granting requests. healing or attesting to agreements. Each decision or resolution is literally nailed down in the figure.
A certain class of nkisi, called nkondi, are able to enforce the solutions they provide actively and to seek vengeance against those who heed them not. These figures either menace the viewer with spears and fierce facial expressions, or strike intimidating, belligerent poses.
Nkisi nkondi specialize in different areas of life. The most important nkisi nkondi carries out mangaaka, or preeminent justice.
Surveillance or watchfulness assist the effective enforcement of the power figure’s decisions. This is registered in the size of the eyes or, in some cases, by multiple sets of eyes. The rope wrapped around some figures represents a snake, a watchful predator who lends its powers of observation to the figure. Double-headed figures have double the visual powers and can see into the city of the dead and the realm of the living at the same time.
Each power figure has a distinct personality, ranging from contemplative to angry to soulful to reserved to compassionate. The ability to suggest those qualities visually with such immediacy and precision is one of the most impressive aspect of the surviving figures.