Far Realm

The Far Realm is a plane of existence that connects to the Material Plane.

During the events of, Vox Machina was told by Clarota that, should they try to enter through the rift to the Far Realm that they found in the Underdark, their minds would break.

It is said that those who have nightmares on the borders of the Far Realm "sometimes dream things into being."

Creatures
The Far Realm is home to "terrible, formless, ancient creatures that may have existed before Exandria itself." The Far Realm is home to various aberrations:
 * Beholders
 * Cloakers
 * Aboleths

History
The Dawnfather and the Everlight banished the Crawling King to a sliver of the Far Realm that borders on the deepest pits (or very base) of the Underdark, "where the boundaries between the worlds grow thin."