This text is written in Common and is entitled An Ecology of the Planes, written by Garth of Suzail, dated 1354 DR. The tome discusses the existence of different sorts of creatures and environments across the known planes of existence. A key passage from the book reads as follows:
The "diffusion theory" has often been invoked by philosophers to explain why creatures on planes totally removed from each other should be biologically indistinguishable. The most commonly held version of the theory asserts that each creature arose—whether this be by evolution or no—on a single world. Then individual creatures somehow were removed from their home plane and transferred to others, where they thrived. The necessary removal is speculated to occur by various means: spontaneously opening gates (or "fistulae," to use the term commonly in vogue), purposeful attempts at "cross-pollination" performed by plane-traveling sentients, accidental transfers (as when a pack animal or a pet escapes on an alien plane), or even divine intervention.
(There is a more extreme version of the diffusion theory that will be discussed in more depth later in this text. It holds that one single plane is the source of all life, and that creatures diffused throughout the multiverse from this source.) At first glance, it would seem that the diffusion theory can be proved or disproved by close examination of the fossil records of several planes, searching for traces of a certain species. If evidence for the evolution of that creature occurs on one plane but not on others, then surely the diffusion theory would be proven. Unfortunately, however, there is not one explored plane where the fossil record is anywhere near complete. There are puzzling gaps, anomalies, and even apparent reversals of causal events, which make us question how much we will ever be able to learn categorically from fossils.
And here the conversation must turn to dragons, for in these species the diffusion theory seems to be the only suitable explanation for their widespread existence. Dragons are the only creatures for which there exist archetypal forms. In dragonkind, these forms are Bahamut, the Platinum Dragon, and Tiamat, the Chromatic Dragon. All of the "core" species of dragonkind—the good-aligned metallic dragons and the evil-aligned chromatic dragons (ignoring for a moment those fringe species like crystal dragons) seem to be pale reflections of their archetypal forms, displaying some but not all of that archetype's characteristics. For example, a red dragon possesses some but not all of the characteristics attributed to Tiamat, while a gold dragon possesses some but not all of the characteristics attributed to Bahamut. Indulging in mathematical language for a moment, each species of dragon seems to be a subset of properties belonging to one or other of the archetypes. Or, conversely, each archetype seems to possess a superset of the properties possessed by the appropriate class of dragonkind.
Some sages truly believe this observation to be representative of the truth of the matter. According to this theory, the very existence of the two archetypal forms—Bahamut and Tiamat—is responsible for the existence of dragons throughout the multiverse. In metaphorical language, dragons are the shadows that the archetypes cast across the planes. As shadows are, in a sense, subsets of the creatures casting them—as they must be, since shadows are two-dimensional—so are the "shadows" of the dragon archetypes subsets of those archetypes' characteristics and powers. (The shadow analogy is actually quite an elegant one. At your leisure, examine the shadow cast by a simple object such as a cube. Depending on the viewer's orientation to the cube and to the surface on which the shadow is cast, the shadow can take the form of a square, a rectangle, a parallelogram, or more complex polygons. This simple experiment shows how different shadows of the same source can be as different as a green and a red dragon.)
Is it any wonder that many dragons worship the archetypal forms? If this theory of shadows is true, then the archetypes truly are the creators of dragonkind, although the sense of creation is diluted in this case, since it seems to lack the aspect of an act of will.
What are the consequences if this theory turns out to be correct? One possibility arises from a consideration of the analogy used earlier. Eliminating shadow—as by shining a light on it—has no effect on the creature casting the shadow. But what is the effect on shadows when the creature casting them is removed from the scene?