Excerpt from "A Dissertation on the Realms," by H.R.M. Thansor.

Chapter 11, introduction.
"Those who have been reading this work diligently will recall that there is some debate over whether or not Nisentil or Firengot should be labeled as the Fifth Realm. I personally believe that the process of entering Nisentil is far more difficult than entering Firengot, and thus, I am considering it as the fifth.

Nisentil, like the Second and Third realms, can only be entered at a certain time. Once every ten years, for a period of one week surrounding the spring equinox, portals may be opened freely during any time of the day. Due to this fairly tricky amount of time, it was only discovered within one hundred years of penning this work, and thus, not a great deal of exploration has been completed.

I, myself, was on the fourth expedition into this barren land. For that is what this land is: barren. In the entirety of the explored realm, there is not a single plant or animal left alive. Ancient ruins, left behind by the people who came before, do contain preserved bodies, allowing us to know that the former residents were bipedal, and likely very much resembled humans. What happened to this land is unclear, as we have been unable to find any records left behind by the ancient civilization. Or, rather, we have been unable to read them. Scattered across the land, located in the ancient ruins, are thousands of small glass objects. They have been infused with metal, and for many years were suspected to be scrap. It was a man on my expedition who suggested that they may have been how the residents kept records, through some sort of magic that we aren't familiar with. Upon his suggestion, we brought several of them back to the Wizarding Academy, where studies still continue on these objects.

As with other time-sensitive realms, portals opened anywhere across Calsin will connect to a single location, known as The Redoubt. As its name suggests, the location appears to be a military base of some sort, long since abandoned as the inhabitants of this realm perished. Conversely, all portals opened from Nisentil will lead to the summoning room in the Wizarding Academy. It is thought that this is where the first portal was opened, thus locking the location, but it is unknown if this is certain. The Redoubt itself is simple, though this may be a result of countless years without habitation. Several old, metal buildings stand surrounded by tall, metal walls. Rust covers everything, confirming that many countless years have passed. Outside the walls, there is an expanse of perhaps two hundred feet, before a large stone walls rises up out of the ground. A single road, paved with a black stone slab, leads out, towards an enormous set of ancient ruins.

The ruins only serve to confuse the scene even more. It is most certainly an ancient city, with every building being made of metal and glass. However, these ruins are no ordinary structures. They rise hundreds if not thousands of feet into the sky, an achievement that I suspect not even the dwarves could attain. Inside these ruins, metal maps have been found on walls, indicating that there are hundreds more cities just like this one. However, the limited amount of time that the portals will open simply doesn't allow for a more extended exploration. Unlike Torsorn, there doesn't appear to be any great threat to life now, but the lack of any form of life (and the inability for transplanted plants to take root in the dead soil) means that no explorer could possibly survive the ten years until another team made it back."