How I Stopped Worrying and Learned to Love Eberron
The Realm of Dreams. Dal Quor is a unique plane in that it is shaped by the dreams of the inhabitants of the Material Plane. Every tree that you dream of sprouts in Dal Quor, but every nightmare monster lives there as well. Because of these principles, the plane is an almost constantly changing place, where no terrain is permanent. The inhabitants of the plane are mostly the quori, coalesced around the Dreaming Dark.
The plane came into existence when the first being slumbered and allowed the energy of their mind to escape the Material Plane. As the total number of dreaming creatures has increased, the plane’s power and size has increased.
Most planes manifest themselves physically on the Material Plane, but because of Quori Giant War, Dal Quor has been forceably disconnected, and any cotermination is probably millenia away.