The Ethereal Lay is the official term for one of the overlay realms, which is sometimes referred to as the Dream Lay, Supernal Lay, or Old Lay. It is a place only accessible by magic or with the help of psychedelic substances. It was believed that this was where lost ghosts, visions, nightmares, dreams, and memories existed simultaneously. It is named so because everything in it does not seem to have a physical form. Note that this is different from the Moon Lay, which is also not of the physical realm.
The Ethereal Lay was inadvertently created when the god Helirend made the stars. As such, the stars give of themselves to this lay.
Use in Magic
Those who practice the art of Perciperation, such as the I'dinar and some Eari and Draol, could visit the Ethereal Lay to access memories and visions.
It should be noted that magic cannot be used inside the Ethereal Lay, only to get there, and any creatures with magic within the Lay could not be harmed there, such as by wraighs or Eari Stones (wraighs cannot travel there). One's physical body in the Material Lay could still succumb to the effects of the wraighs or Stones, which would trap kill them in the physical plane. This differs from those killed while inside the Moon Lay, which makes them into Nightwraiths. Staying too long in the Moon Lay would also yield this same effect.