The Heroes of Feather Falls
The First World is so called because it is believed to be the gods’ first draft of the subsequent plane which would later split into the Material Plane and the Shadow Plane.
It is coterminous with the Material Plane and the Shadow Plane, but exists outside the standard cosmology, being somehow “behind” the other two planes.
Appearance and Characteristics
The First World is an infinite plane of constantly varying wilderness – mountains, forests etc. It epitomizes the chaos of birth and fertility. Conditions vary dramatically from place to place. What would be considered to be laws of nature on the Material Plane are no more than local by-laws in the First World, and even these by-laws can be overturned (even unconsciously) by those with sufficient willpower. Times and distances are unreliable in the First World.
Areas of stability do occur. In some cases this is apparently a random event; a current of stability flows through the First World, leaving behind an area of certainty which might range from a narrow trail a pace or two wide up to a vast swathe hundreds of miles across. These stable zones eventually decay back into the natural uncertainty of the First World, a process which might take hours or centuries. It may be that these are gradually increasing in duration.
More commonly, stable areas exist where there is a connection to the Material Plane. Stability seeps into the First World at these points, much to the disgust of the locals, who seek to repair the damage and punish those they consider to be responsible.
Of course, this is a two way process. The fertility of the First World also flows through the connection into the Material Plane, with unpredictable results.
The First World is home to all manner of strange creatures, apparently prototype versions of the plants and animals of the Material Plane. However, the chief inhabitants are the fey. The most powerful of them are the eight (formerly nine) creatures known as the Eldest and their fearsome living weapons, the Tane.
Some of the other races found on the Material Plane also have counterparts in the First World. It is widely accepted that gnomes migrated to Faerun from the First World during an age long past, but some gnomes did not make the trip and are still here.
Linnorms roam the First World, and claim that the Material Plane’s dragons are the descendants of linnorms who crossed over in the distant past.
However, what all the natives of the First World have in common is that (barring extreme circumstances, such as the intervention of powerful magic) they do not die when on that plane. Those who are “killed” reform in time from the substance of the plane.
This discourages them from visiting other planes – since they do not reform outside the First World, but are also not eligible for any form of afterlife – and can also make them somewhat reckless when it comes to lives in the First World (including the lives of visitors, which can have tragic consequences).
Almost all creatures in the First World that can speak can do so in the First World’s nameless common tongue. It is similar to both Sylvan and Aklo (to such an extent that visitors fluent in either language can generally understand it) and may have been the root language of both tongues.
The inhabitants of the First World lack souls, and so are of little interest to the gods. They also have little interest in the gods either. A few of the First World’s inhabitants may be living here in order to avoid the wrath of an offended deity. Visitors from other planes sometimes report they feel disconnected from their gods. Divine magic still works, however – although whether this is solely due to the faith (i.e. will) of the spellcaster, or because the gods have not completely abandoned the First World, is a matter of conjecture.
Connections to Faerun
There is a substantial rift linking Faerun to the First World in the Moonshaes, which explains that region’s large fey population.
Another overlapping of the First world exists deep within the ancient woods of the Elven Court, in Cormanthor. The barrier here is not a constant two-way portal, but is instead a malleable membrane, thinner in some places than others, allowing knowledgeable and capable travelers to pass between the worlds.