Far Realm

The Far Realm is a plane that connects to the Material Plane, generally deep in the Underdark.

When Vox Machina found a rift to the Far Realm near Yug'Voril, Clarota warned them that, should they try to enter, their minds would break.

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

Inhabitants
The Far Realm is home to a Betrayer God Torog and to "terrible, formless, ancient creatures that may have existed before Exandria itself", including various aberrations: aboleths, beholders, and cloakers.

History
Arriving through a portal from the Far Realm millennia before the Calamity, aboleths and other aberrations conquered the Underdark beneath the Bladeshimmer Shoreline and drove their slaves to build their capital: Salar, the Unseeable City. They slowly began expanding toward the surface, and their psychic energies gradually produced the azuremite of the Crystalfen Caverns. The final battle of the Calamity sent strong waves of magical force through Exandria, unintentionally causing the collapse of most of the Crystalfen Caverns and the fall of the aberrations' civilization there.

During the Calamity, 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."

A rift to the Far Realm also exists near the ancient city of Yug'Voril deep in the Underdark, and Vox Machina saw veins of blue crystal reminiscent of azuremite in the cavern walls near the approach to the city. The city's original builders are long gone, and the city is lately controlled by illithids. A beholder named K'Varn emerged from the rift with a Horn of Orcus and took control of both the illithid colony and the Emberhold for about four months until Vox Machina and Clarota killed him.

In Blightshore, a sinkhole of untold depth called the Miskath Pit blends the Underdark with the Far Realm.

The Netherdeep is described as a cross between the Far Realm and the deep ocean.