Which oracle commands the priestess that Unoka consults in Things Fall Apart?

The priestess is a woman who communes with a particular oracle or god. The priestess could commune with the dead whom had been committed to the earth.

For most of the book, Chielo is the priestess of Agbala, the Oracle of the Hills and Caves, for Umuofia. In earlier times, a woman called Chika is the priestess.