Excerpt from "A Dissertation on the Realms," by H.R.M. Thansor.
Chapter 4, introduction. "Known throughout Calsin as the 'Dark Realm,' there is perhaps no other name that could provide such a misconstrued view of the Second Realm as this. The proper name, as known by my fellow mages and learned scholars through the land, is Darsendor. It is easy to see whereby Darsendor comes by its colloquial nomenclature, but this by no means excuses the filthy excuses for wizards that propagate such nonsense.
Darsendor intersects our own realm more closely than any other known plane of existence, thus granting it the title of 'Second Realm.' It makes its closest approach every single night, once the sun has set and the creatures of the night have emerged. Once the world has gone dark, portals between our two planes of existence may be opened. The magic behind this transformation is complex and, admittedly, not fully understood. We believe that the sun's light breaks the bond between our two realms, though this does not explain why portals cannot be opened in deep caves during the daytime. Much more research will be needed before the bonds between our two worlds can be understood.
Darsendor itself is a unique realm, not bound by many of the constructs that we take for granted in Calsin. For example, everything in the realm weighs less than it does on Calsin, including any individuals that happen to enter. After careful experimentation, the ratio of weight on Calsin to weight in Darsendor is approximately 2.5:1. Additionally, Darsendor does not seem to have any discernible end. Calsin is a single body of land, surrounded by water. While it is, indeed, likely that there is more land beyond the water, it is extraordinarily unlikely that the water continues forever. Darsendor, however, is a simple rocky plain that extends as far as the eye can see. Simply standing on the ground, you can see much farther than is possible on Calsin. Additionally, upon climbing a mere dozen feet into the air, it is possible to see structures a thousand miles away. Because of this, it is unknown just how expansive the native troll population has become. Should they ever decide to invade the realm of Calsin, the forces that they could bring to bear would likely be far greater than we could possibly stand against.
As was stated above, the environment of Darsendor is bleak. There are no known plants native to the realm, though that may be simple deception on the part of the trolls. The rocks there are varied, perhaps even more so than the minerals from Calsin, providing powerful magic for our dark elven brethren. Additionally, the sky of Darsendor is almost pitch-black to the human eye (though both dark elves and aqahartis claim the ability to see quite clearly). It is probable that their magic, along with the magic of the trolls, allows them to see light that is invisible to other species.
Though it is understandable to be fascinated by Darsendor, it is advisable not to become too infatuated by the Second Realm. Its inhabitants are dangerous, and spending too much time in the land can result in adverse effects upon exposure to our sun once again. While we do know much about the realm, it is advisable to steer clear of any practices related to Darsendor, and leave its exploration and understanding up to the experts."