The void lords in the Warcraft Universe are monstrous entities composed of pure shadow energy who rule over the Void, outside the borders of reality. Merciless and cruel beyond imagination, they seek only to twist reality into a realm of eternal torment, and ultimately to devour all matter and energy and the universe itself. However, only the most powerful of the void lords can actually manifest in the physical universe, weakened, and only for limited amounts of time, for their energies quickly seep into nothingness. They must therefore consume untold amounts of matter and energy to maintain their presence.
From the moment the physical universe was born, the void lords had been watching the titans. Envious of the titans' power, the void lords attempted to corrupt one of them, but the titans remained impervious to their attempts. Instead, the void lords pooled their power and hurled dark, parasitic horrors — later known as the Old Gods — out into the universe to find and exert their influence over titan world-souls.
Dimensius the All-Devouring was a void lord who manifested in the physical universe.