Oblivion, also called the Void or the Abyss, is an active force of annihilation that lies beneath the Underworld. Everything that enters into Oblivion is destroyed utterly; it is the ultimate nothingness.
Oblivion may have always existed, or, like the Underworld itself, it may have been called into being by the death of a Primordial during the Primordial War. Its mouth lies at the center of the Underworld, beneath Stygia, and it exerts a steady pull on those souls who do not or cannot enter the cycle of reincarnation. That pull is counterbalanced by the strength of the soul's fetters, allowing ghosts to dwell in the Underworld without plunging straight into Oblivion. The Neverborn are fettered to Creation itself, and are thus trapped forever on the edge of Oblivion. Between the surface of the Underworld and the heart of Oblivion lies the Labyrinth, a twisting network of tunnels and caverns haunted by spectres and other beings that serve Oblivion without being consumed by it.