The Moon Lay is one of several overlay realms, which is sometimes referred to as the Lunar Lay. It is considered a sort of "in-between" realm, like a reflection. The Moon Lay can be accessed by creatures in the Material Lay through the usage of standing liths called Ghost Rings, which have the ability to concentrate moonlight enough to allow passage. Those who could do this were called Moontreaders. There are also creatures which exist in the plane, such as the wraighs. Likewise, it is possible to summon some to the Material Lay; those of the Tal Calar do this.
Magic in the Moon Lay
It should be noted that magic cannot be used inside the Moon Lay, and any creatures with magic within them could not be harmed within the Moon Lay, such as by wraighs or Eari Stones. One's physical body in the Material Lay could still succumb to the effects of the wraighs or Stones, which would trap them forever in the Moon Lay, making them Nightwraiths. Staying too long would also yield this same effect. Creatures in the Moon Lay can sometimes be seen and heard in the Material Plane when the moon is out, and cannot interact with ordinary physical objects. They can, however, use special objects that have been properly enchanted, such as weapons.