Also known as kormahn in D'ni language, a Descriptive Book contains the primary description of a world written according to the principles of the Art, establishing the founding link to one of the infinite Ages in the Great Tree of Possibilities. The process of describing the Age focused on avoiding written contradictions which would result in a link to an unstable Age. A Book with contradictions would attempt to link to a quantum reality that matches a contradictory description, and the closest thing it could "find" would be an unviable or unstable Age.