Realms
The knowledge that there are realms beyond our own is older than recorded history. All around the world and all through time, people have learned how to find the natural connections between the realms and how to manipulate them. This knowledge has brought wisdom and power to some, and death and destruction to others.
As might be expected, the quality and quantity of information available varies greatly. Investigators are reminded that the majority of our knowledge regarding other realms is based upon their reports. If there are any errors or omissions, the corrections should be submitted using the appropriate protocol.
The Nature of Realms
The simplest description of the realms is that they are worlds like our own. Although this is somewhat true, it greatly understates the many differences. For example, some are, as best as can be determined, natural in origins, but there are realms that have clearly been created through the use of arcane forces.
Physical Realms
Physical realms are generally like our own. They may be inhospitable or even deadly, but they are tangible. The creatures that inhabit physical realms are often exotic, but they generally live and bleed like those with which we're familiar.
Scale
Some of the realms that we know about are as vast as our own or perhaps even greater, others can be explored by a day's hike, and still others are scarcely the size of a park. The largest realms have what might be called "natural" skies. These are similar to what we see, with a sun during the day and stars at night. The smallest often have skies that are perpetually overcast or with an unvarying appearance, much like a painted ceiling.
This variation has led some theorists to speculate that what we think may be multiple realms might actually just be very large like our own world. Those who argue for this point out that the variations in inhabitants and climate might simply be a factor of latitude and longitude. After all, their reasoning goes, would a visitor who saw first saw the fjord region of Norway and then was whisked to the deepest jungles of Africa not imagine that they've stepped into two different worlds?
When pressed on the question of portals that lead from one of these realms to another, breaking the apparent law that portals cannot connect two locations in the same realm, these individuals wave this away as an example of an excessive devotion to empirical evidence.
Physical Principles
The nature of physical laws varies between Realms. In some realms, even things as fundamental as time and space function differently. An example of this phenomenon that many members of the Service will be familiar with is that distances in Fairweather can be extremely deceptive. This is particularly true when the viewer is moving.
In other realms, arcane forces function differently than in our world. They may have greater or lesser effect, or the effects may not be what was expected. The goblin markets demonstrate this, with their muting of the power of arcane objects.
In all cases, Service members are advised to exercise extreme caution and to make no assumptions when travelling to other realms. Anyone returning from another realm is required to file a report describing what they observed and any ill effects suffered.
Æthereal Realms
The æthereal realms are utterly unlike our own world. It's not possible for a physical creature like a human to survive a visit to one of the æthereal realms, so all of our knowledge about them is second-hand at best. Whether there is one æthereal realm or many remains pure speculation. The more theologically inclined favor the multiple realm theory.
Nature
Unlike our realm, which is comprised of elemental matter, the æthereal realms consist entirely of æther. Æther is poorly understood, but it appears to represent some form of fundamental material through which energy flows. At present, it is unknown whether this æther is related to the luminiferous æther of the physical world, through which light flows, but current science indicates that the latter is a special, limited form of the former.
Individuals who have been possessed by occult creatures report memories of an endless black void, speckled with glowing shapes that appear to be the creatures of the realm, and laced with crackling lighting that dances between these things. It is unknown whether these images accurately reflect the nature of the realms or if they are merely the best approximation that a mortal mind can muster.
The Occult
While physical creatures are unable to travel to the æthereal realms, æthereal beings are able to enter the physical realms under certain conditions. This phenomenon falls under the occult sciences.