The Void is the plane where the Vishmiir are banished. The Vishmiir are a very ancient kind of non-corporeal undead whose power is tied to darkness. They are extremely powerful and able to act across vast distances. When they were attempting to make all the world cold in 5102 Modern Era, saying their name out loud would focus their attention, and they would drain life or the head of the person speaking it would explode. They were able to possess people, and individual vishmiir resembled eidolon. They were once again banished using a chalice and crystal, artifacts collecting the power of life energy.
[The Void] All is cold and still and utterly lifeless. Faintly shifting shadows are all you can see. Also here: the body of XXXXX who is lying down, the body of YYYYY who is lying down Obvious paths: none.
Bodies were pulled away to this place after being killed by vishmiir, similar to the death mechanics with Purgatory. The Vishmiir had "no central source", existing everywhere and nowhere, and as non-corporeal undead only partly existed. The Void was breached during a Lornon's Eve event, and it is believed Fash'lo'nae may have been responsible to see what would happen. They intended to plunge the world in darkness, where they would manifest within it freely. This suggests the plane is in some sense coterminous with ours as they were collectively aware across the continent simultaneously.