The origin of the Hellscape is unknown, the only place that contains such knowledge is within its borders and is thus corrupted by its very nature. Some scientists have thus proposed that it is unknowable, and various attempts at advanced information retrieval have helped to confirm this. What few things that are known about it are the result of Legion experiments during the few times that proper tools have been available within it's confines.
What makes the Hellscape unique is that within its confines, the POE of any object or entity is much lower then it would be in normal space. Because of this, the Extemos cannot survive in this dimension, the rapid reactions with their makeup quickly falling prey to the lack of certainty and the Extemos dissolving.
It is believed that the Hellscape has existed since the birth of the Gods from the maelstrom, and has grown in size and influence in direct opposition to the creations of the Gods. It was first discovered shortly after the founding of the Legion, when small creatures of an irrational nature would be found within the reactors of interstellar vessels. The Watchmaker determined that these were not the creation of any God or Diety and they were in fact from another plane of existence, further cementing the theory Heaven existed. As the Legion expanded its exploration endeavors, certain rare areas of space were encountered that acted as portals into the Hellscape, from which few returned. Most of these dissipated after their discovery, but there is one continuous anomaly that has been definitively recorded, Planetoid Delta.
The Hellscape is normally set apart from the rest of the universe, a barrier of some indescernible nature preventing the flow of energy and matter between our universe and the Hellscape. It has been noted, however, that this barrier weakens at points with high energy densities, such as Hyper Nuclear Reactors. Something such as a Sun is at the threshold of energy density necessary to allow flow between this universe and the Hellscape, with greater densities tearing greater holes and allowing larger entities to enter through. The Generator seems to be immune to this effect however, as it stabilizes nearby space-time as a result of its energy production process.
Within the Hellscape reside entites with the ability to alter their personal realities at will. Due to the chaos of the dimension they live in, they tend to be extermly flexible in their worldview, able to change the way their very minds work in conjunction with the physical changes that cascade throughout the Hellscape. Their strength is based on their essence, which translates over to physical power when they are present in our universe.