Unexistence is the extremely strange thing that lies beyond The Far.
Unexistence is at a strange point in the hierarchy, containing a verse with an ill-defined size, and being contained by a ridiculously huge complex. That has caused existence and reality to begin to break down. That makes the Unexistence "not exist", hence the name. The picture only shows a wormhole to Unexistence, because an actual image of Unexistence would be impossible.
Only a few creatures have ever been to Unexistence. All never came back, most likely due to the space inside Unexistence having no "existence coordinates" , which basically tell where, when, why, and how a place exists within the cosmos. Since Unexistence doesn't have any existence coordinates, it can basically erase any creatures out of existence if they enter it.
It is unknown what lies inside of Unexistence except for at least one Far.
Other than our Local Unexistence, there are many more such anomalies scattered everywhere throughout the hierarchy.