Many scholars categorize the realm of Nar-Voth as the unclaimed wilderness of the Underdark, with its vast amount of unexplored regions and preponderance of tribal societies like the orcs, ice trolls and frost giants.
To these scholars, Sekamina is then the heart of Underdark civilization, although a civilization that values fear, rewards cruelty, and exists only to further its own needs at the expense of others.
Although these scholars have heard of Orv, the third realm of the Underdark, most know little more than legends of this fabled land. The races of Sekamina and Nar-Voth know little about Orv as well, and what they do know strikes fear even into their darkened hearts. If Nar-Voth is the wild, and Sekamina is civilization, then Orv must surely be Hell.
Orv’s genesis is not in the natural world, for the vast vaults of strange environments and closed ecosystems is not something a sane world could produce—left to nature, Orv would collapse into a realm of isolated deadend tunnels filled with poisonous air or solid masses of stone grown pliant and soft from the searing heat. Yet this is manifestly not the case, for Orv is the most varied and immense Underdark realm of them all.
Orv consists of dozens of immense chambers called Vaults. The size and shape of each vault varies greatly, yet none are smaller than the smallest kingdoms of the surface world. Most are, in fact, much larger. Some, such as the Sightless Sea itself, contain entire oceans, but the majority of the Vaults of Orv are somewhere between the two extremes, immense caverns thousands of feet in height and covering regions large enough to contain entire nations. Each has its own rules, its own environment, and its own masters, its own dangers.