Physically, Ombwiri are usually white, like a ghost, and only visible to the initiated. They can inflict illness and misfortune if they wish, or bring wellbeing, wealth, etc, if they deem it appropriate. Somewhat fickle characters. They demand the cooperation of their chosen descendant.
Ombwiri function as guardian angels for a number of tribal groups in central Africa, particularly in Gabon. They are usually identified as ancestor spirits, who take a personal interest in the affairs of their descendants. The Ombwiri (sometimes spelt as Ombuiri) can appear in dreams, in visions, during initiatory ceremonies where mildly narcotic herbal preparations are consumed, during illness, or as spontaneous visions available to adepts of the Ombwiri cult. The nuts and bolts of Ombwiri experiences are presented in a series of articles by Stanislaw Swiderski in the journal Anthropos. An interesting semi-fictional account by Laurent Owondo called Au Bout du Silence is published by Hatier in Paris (1987). In a way, there is some similarity to the small still voice of mosaic prophets.