The Art (D'ni language: Rehgehstoy) is the term properly used to refer to the D'ni study and mastery of The Skill: the ability to write special books that describe and link to Ages, or different worlds.
The origins of the Art are lost in the times of Garternay, and it was believed by the D'ni to have been delivered to the Ronay (the ancestors of the D'ni) by Yahvo the Creator. There are many legends about the origin of the Art, but all are conflicting. One of them wants the first Guildmaster being Varsil who created the Food Age of Dania; the D'ni civilization was based on his work.
Procedures and Methods
The description for an Age is put into a unique Descriptive Book, written in a special form of the D'ni language and using special Books and Ink. Only one Descriptive Book can exist that links to a given Age, but there can be multiple Linking Books to the same Age.
Linking Books have a viewing panel called a linking panel that shows a picture of the target location. The panel is interactive: by merely touching it, the person is linked to that Age.
Types of Ages
Certain D'ni Masters (as well as Atrus) favored the "cluster design" philosophy; first writing an Age that will serve as a "hub world" which then, by housing linking books to related Ages, will serve as a central link to them. J'nanin was a classic example.
The majority of D'ni believed that all Ages were actually created by the Maker, and when a writer writes a Descriptive Book, a link is established to an extant Age, approximate in character to the Age described.
The Art, in all its complexity, had elegantly simple essential underlying principles.
The Art is actually the science of putting down a precisely structured equation of words. Every equation needs as its foundation an underlying concept around which the Age can develop.
Anna taught Atrus that energy was the underlying fuel that powers all activity. By tapping into its latent energy sources, an Age moves out of stasis to growth and development and thus is necessary for life. However energy can have diverse forms, each with strengths and weaknesses of its own. Anna also often pointed out that civilizations are stimulated by balanced systems.
Atrus experimented with the Art by writing around concepts that intrigued him each time, and then exploring the and discovering how the Age manifested the results of that concept. Sometimes civilizations had arisen, sometimes not, depending on what concept the Age embodied.
Growing up under his grandmother Anna's guidance, Atrus developed into a deeply ethical man with considerable respect for life and moral values. Because of this, many of his Ages reflect this and all are usually balanced in the natural elements, and the cycle of life and death.
There have been some restrictions regarding writing "bizarre" Ages, that would defy certain laws of nature, as apparently these might create links to unstable Ages. However Atrus has been known to write such Ages for experimental purposes, such as Gravitation. Catherine's Ages such as Torus and Serenia were thought by Atrus to defy the rules of science.
It seems that the D'ni had experimented with writing artificial objects in their Ages. However, the attempts were unsuccessful and the results unpredictable, and restrictions were established to avoid these problems. Atrus attempted to violate this rule by writing a ship in Stoneship Age resulting in a ship broken and fused into an island. However later Atrus and Catherine were successful in writing nara linking chambers into Spire and Haven.
Writers cannot just write down anything into a Descriptive Book and create a Link to a suitable (as the D'ni say "stable") world. There are many rules that ages must abide by to be considered stable by The Guild of Maintainers. Because of the enormous work needed and responsibilities required to create a link to an Age, the Art is often considered a daunting task to many D'ni, and writing Ages is generally approached with much apprehension and sometimes even fear.
Written contradictions, that is, putting down phrases in the Descriptive Book that cannot all be true, are the biggest mistake one can make in writing. This is usually done accidentally, but the results can be disastrous, as such worlds can be extremely unstable and thus unsafe to travel to. For this, attention in writing is of great concern and from a young age, Guild students were taught to focus on the details before writing, so as to avoid contradicting this information later on the book. Stories abound of preliminary scouts from the Guild of Maintainers who discovered contradictions when it was already too late, and never returned.
Some Ages such as Riven are unstable because of these contradictions, however the nature of these contradictions means that the Age slowly deteriorated and it was not evident that the age was dying.
Only members of the Guild of Writers were taught and allowed to write descriptive books, and one of the Guild of Maintainers's jobs was to ensure the Ages' stability. Furthermore, there was a belief that the Art was reserved only for the D'ni race, and there were lively debates among the D'ni about this subject.
Abusers of The Art
Some writers have sought to abuse the power of the The Art, either by using their power as 'creator' to establish a domineering and god-like rule over an Age or Ages, or by using the power of The Art for material gain (i.e. enslavement of native peoples).
Some well-known abusers of The Art are: