Negative Energy Plane
It is the blackest night.
It is the heart of darkness.
It is the hunger that devours souls
Cosmologists believe that negative energy and its opposite positive energy, combined with the four elements, make up the known universe. This plane was extremely hostile to all forms of life and energy. Only the undead could travel with impunity here, and the more powerful undead could harness this death energy to attack the living with devastating effect.
The Negative Energy plane could be reached via the Ethereal Plane or an adjacent elemental plane, but not by an elemental vortex, as is possible with the Elemental Planes.
Such was the influence of the Negative Energy plane that the boundary it shares with the Ethereal Realm was weak and fluctuated randomly at times. Travelers thinking they were safe staying in this border Ethereal could suddenly be dumped on the Plane of Death some distance from the rapidly receding border.
This plane is described as being an airless, featureless void of darkness with gravity being an individual choice. Somewhat paradoxically, structures existed on a landscape of sorts, either made of the physical, solid darkness, or perhaps of elemental earth that could survive in regions of the plane (called doldrums) that did not exhibit the major-negative dominance trait. The atmosphere was not vacuum but could not be used by winged creatures for propulsion, nor could it sustain life, yet torches and lanterns would burn for a short while before being extinguished. Magical light sources worked as usual but visibility was extremely limited. These characteristics led cosmologists to speculate that it was the energy-sucking nature of the plane that greedily devoured any life-giving energies rather than the complete lack thereof, but the difference is of interest only to sages. In practical terms, without protection from the negative energy and elimination of the need to breathe, death was only a few minutes away at best.
Just as there were areas where the negative energy seemed to recede and create the doldrums, some locations exhibited concentrations intense enough to create stable chunks of solid matter that were dubbed voidstone. These absolutely black blobs ranged from a few inches/centimeters in diameter to the size of a small house and perhaps larger. Anything that touched a voidstone was destroyed in the span of a few heartbeats—even the undead were not immune. This property led scholars to speculate that voidstone may have been a component in the creation of magic items like the sphere of annihilation. Another curious and deadly property of these silent death traps was that voidstones of a certain size, not too small and not too large, were attracted to life and would move toward the nearest living creature in jerky, uneven leaps. The exact range of this attraction was unknown because of limited visibility, and all reports of attempted mental control indicated failure. It was discovered that undead creatures could survive here and that powerful undead, such as vampires, liches, wraiths, wights, and spectres, made this plane their home base. And where undead are found, necromancers are seldom far behind. The doldrums were best suited for necromantic work but there was always a danger the negative energy would surge and overwhelm the area.