The Reality and Usage of the World of Souls

The World of Souls is a distinct reality, tied to the material reality in means that allow its seepage into the universe.
The World of Souls is by nature difficult to understand. Although aspects of its dimension are able to enter into our material reality as matter, the opposite is not true. Although, given the opposing natures of the two realities, it is worth noting that this is likely due to how the two realities ought to interact. The World of Souls, immaterial in nature, cannot receive matter. Our reality, meanwhile, as a material realm, can only receive such things. This is evident when a psionically gifted individual attempt to martial their connection to the other dimension. Their desires- their thoughts- bring into our reality what they had wished to, assuming that they are successful. With this demonstration, it seems to be clear that the relation between the two realities is characterized by matter on the one hand and thought on the other. The bond between the realities is the Soul, which every member of every sapient species known possesses. For instance, a Human would find themselves resident in both realities at once- bodily in our universe, while their soul and likely the origin of their consciousness is found in the World of Souls.
This connection of the individual allows one's body to draw forth the essence of the World of Souls into the Universe as matter or energy. A common means of imagining this is via the creation of things such as fire, water, or electricity. Although the more proficient can use their talents to draw forth concussive forces and worked metal. The effects of this means that segments of the population become more dangerous and are usually seen as a resource to be developed by the state, as these Psionic individuals are very important.
Beyond simple "Magic" the psionic connections brings other benefits. One of these is the navigation of the Express, which is possible due to the insight of these individuals. The manifestation of the Express is, after all, due to the World of Souls and the spread of sapient life. These pathways are well-known, and accessing them with a starship is easy enough, but maintaining a steady path on them over the course of light years is a near impossible task without someone guiding the course psychically. For this reason, these individuals can typically find an open job throughout the galaxy on ships helping to guide trade vessels or to lead armed naval vessels at war.
One, ominous, note about the nature of the World of Souls is its seeming necessity of equilibrium of some sort with the physical universe. While there exist sapient beings which dwell within both realities simultaneously, there also exist entities within our reality which do not exist in the World of Souls such as animals or plants. It would stand to reason that there exists, then, such mirrored entities within the World of Souls. Entities that only exist within the World of Souls, but that perhaps could grow to a point in order to exist within the physical universe. Indeed, from what records remain of their mention, the Ethereal Horde seems to possibly be just such an existence.