The Dream (Sanctuary's Lot Supplement)
From D&D Wiki
A psychic realm where spirits coalesce, mature, and, in the fullness of time, discorporate back into misty formlessness. While removed from the material realm, The Dream has an enormous influence upon. Additionally, it as the source of all souls, magic, and dreams. Every living creature who has ever dreamed has ventured here, while asleep.
This plane of existence is home the Gods of the Dream, the Lords of the Ten Towers, their legions of servants, and numberless dream spirits.