The Void is the nothingness into which the Dark Lords of Chaos were banished after their defeat in the First Battle. Believed to be infinite and beyond the control of any being, it can nonetheless be accessed and manipulated by certain individuals - the Riddling Reaver was one such individual, with a permanently open portal to the Void in the heart of his retreat, which he used to dispose of more troublesome enemies. How the Void was kept from infringing on the material world through such a permanent portal is unknown.