THE POSITIVE AND NEGATIVE ENERGY PLANES
It's the Positive and Negative Energy Planes that breathe life into, or take it away from, the physical universe. These are the planes of life and death. These are the planes of life force. All the living things draw their energy from the Positive plane, while all the undead creatures draw from the Negative plane. Even spells and magical items based on promoting or taking life tie directly to these planes.
The Positive Energy Plane is a dangerous, terrible place to visit, despite its life promoting nature. Its energy is too strong. Travelers find this plane even more brilliant than the Plane of Radiance. Its energies seep into bashers entering the plane until their bodies simply can no longer contain the energy, literally burning the poor sods out. If a traveler is wounded or injured, the energies of the plane quickly heal the wounds. The only known native inhabitants of this plane are the xeg-ya, creatures of pure positive energy.
There is nothing useful to a planewalker on the Negative Energy Plane. There's no reason a basher would ever want to come here. This plane steals energy and destroys the spirit. It's a black formless plane of all-consuming hunger, feeding upon life energy. Berks who come here without magical protection die and their spirits are consumed forever. Some sodding addle-coves have made it possible to visit this plane. The Dustmen know of secret portals to a citadel that they maintain here, the Fortress of the Soul. Native inhabitants of this plane are the xeg-yi, "beings" of pure negative energy. Also undead such as spectres, wights, wraiths hover on this plane waiting to be loosed upon other planes, where they can drain energy from the living creatures.