The Fagalde Collection of West African Tribal Art - The Nkondi or Nkonde Nail Fetish

Fetishes were protective figures used by individuals, families, or whole communities to destroy or weaken evil spirits, prevent or cure illnesses, repel bad deeds, solemnize contracts or oath-taking, and decide arguments. A diviner or holy person would activate the statue, using magical substances. Fetishes gained power and were effective because people believed in them...
http://tribart.blogspot.fr/2017_02_01_archive.html#4155588619155947780

The nkondi are the most powerful of the nkisi. They were used to identify and hunt down unknown wrongdoers such as thieves, and people who were believed to cause sickness or death by occult means. They were also used to punish people who swore false oaths and villages which broke treaties...

Head of a Queen Mother (Iyoba)...

Head of a Queen Mother (Iyoba) 
1750–1800 - Nigeria, Court of Benin 
Courtesy: The MET Museum of Art

In the Benin kingdom, the iyoba, or mother of the oba (king), occupies an important and historically significant place within Benin's political hierarchy.

The title was first conferred upon Idia, the mother of king Esigie, who used her political skill and supernatural abilities to save her son's kingdom from dissolution in the late fifteenth century.

Ever since that time, queen mothers have been considered powerful protectors of their sons and, by extension, the kingdom itself.

Because of the enormous esteem in which they are held, iyobas enjoy privileges second only to the oba himself, such as a separate palace, a retinue of female attendants, and the right to commission cast brass sculptures for religious or personal use...   http://tribart.blogspot.fr/2017_02_01_archive.html#1755759189924177816