|This article contains canon information corresponding to the Tales of Arcadia franchise. That means all information in this article is true and has appeared/been validated officially on-screen.|
It is referred to as 'the void between worlds' including 'the' and all lowercase letters, as a description of what it is and a conjectural title. It is entered if you are called by the council of dead Trollhunters, and it is unknown if it can be reached another way.
It seems like the Trollhunter training arena except the color schemes is black and blue, and there are arcs and wavy pieces of architecture overhead, and there is no roof—instead, it's an open sky filled with stars and constellations.