The Ritual of Sundering is an extremely powerful ritual that the followers of Agoth, in particular his Vere, use to enable the Realm of Agoth to merge with another place.  The ritual opens up a portal directly to the Void, which allows the all life consuming essence of the Void to seep out and encompass the area surrounding the portal.  How much area is covered is dependent upon the strength of the ritual and the creature performing it, as well as any other enhancements in place – normally it would cover a maximum of 100 square miles, although it has managed to swallow an entire plane before. Once the merging has taken place all life over the area covered is stripped bare and any Souls taken feed the nearest Soul Gardens.