The Volumes of Truth was a religious text of the Jydan religion and its derivative, the Ni'Shaw-Dak religion. It was probably used in other Ka'hren religions.
The Volumes of Truth included the laws and ethic code of the multiple Jydan gods, written by the three prophets of each individual god (as opposed to the other holy text of Jydan, the Jydan Writings, also written by the three prophets of each god but telling the god's teachings).