The substance of the Fade is sometimes referred to as the "ether".
In its raw form, the Fade is a twisted, frightening world of dark rock and raw lyrium veins where it is always night and gravity affects nothing equally. Gaps between dreams are such void places.
An island with the Black City, a shadowy metropolis with twisted spires seems to be the only constant feature of the Fade, always on the horizon. No one has managed to reach it since over-ambitious mages physically invaded the Fade in -395 Ancient. Even the most powerful demons keep their distance.
The Fade may appear as something else entirely when shaped by dreams. Much of the Fade is split up into fiefs or demesnes belonging to the spirits or demons that live there, and they change the landscape of the Fade to emulate what they see in the minds of mortal dreamers. They copy locations, objects, people and concepts of the real world, often in a cruel or confusing way. These copies are nowhere near consistent, and fluctuate according to the movement of the dreamers. Spirits whose realms are flocked with visitors rise to rule great portions of the Fade, while memories and concepts forgotten in the real world slowly drift away back into the ether, the spirits who ruled them losing all potency.
According to Solas, spirits and demons are more alike than most people realize. They are, in fact, often the mirror image of the same being, with spirits unwillingly brought across the Veil by mages having their purposes perverted and becoming demons.
Flora & Fauna
spirits and memories