Rivan Codex Cover illustration by Geoff Taylor

The Rivan Codex by David and Leigh Eddings
The eighth book in the Belgariad series 1998

Before David Eddings wrote "The Belgariad" he spent a year working on the design and mythology of the fantasy world in which it is set. This "Codex" comprises the material which is taken for granted but not spelled out, history, geography, myths and folktales, peoples, customs, gods and more.