The Primal Realm is a sealed off domain of existence below that of normal reality. It is the cornerstone of the material world, and is split into nine regions, The Cornerstone, The Plane of Fire, The Plane of Water, The Plane of Earth, The Plane of Wind, The Plane of Lightning, The Plane of Ice, The Plane of Light, and the Plane of Darkness.
These nine regions are balanced by the Cornerstone, the ancient primordial device that keeps the realm from collapsing, with all of reality along with it. Many ancient and primal beings make residence here.
This is the location where elemental magic comes from, and is the primary source of power for Awakeners.