The Far Realm

The Plane of Madness and Insanity. The home and prison of the Great Old Ones. The Far Realm has been whispered about since the dawn of time. Ages ago, when life began, the Elder Gods and their servants, the Great Old Ones, raged and sought to purge the multiverse of these insignificant life forms. The Primordials and the Gods joined together and tricked the Great Old Ones into a realm of false reality. They then sealed that realm off from the rest of the planes.

However, the Great Old Ones had foreseen their imprisonment and seeded the world with their lore, their servitors and artifacts of their own power. The Far Realm was not forgotten, and through the ages, mortals and immortals alike have been driven mad by their whispers and tried to open the gates and release their masters.
If that would happen, reality would end.
Illithids, beholders, aboleths, kopru and many other creatures are creations of the Great Old Ones and seek the return of their masters. Some say that the original inhabitants of the Abyss, the Obyriths were creations of the Great Old Ones.

Type

Dimensional plane