The Nkaka is an important part of the Bilumbu divination ritual practiced by the Luba tribe. 

Both male and female followers wear it during the trance, which allows them to act as mediums for ancestors or spirits to communicate with onlookers. 

The diviners use their supernatural abilities to interpret signs, diagnose problems, and provide advice to those seeking guidance. The ritual is believed to help people gain insight into their futures and uncover hidden truths.