Location from Solo Leveling by Chugong
The dimension between the human world and the Monarchs' realm — the space where Gates originate and where the cosmic war spills over into Earth.
The Gap Between Worlds is the dimensional space that separates the human world from the Monarchs' dimension. Gates — the dimensional portals that spawn monsters on Earth — originate from fractures in this space. The Rulers and Monarchs have been fighting across this gap for eons, and Earth is simply caught in the crossfire. The gap is not a physical place humans can travel to under normal circumstances; it's a conceptual boundary that the Monarchs are slowly eroding with each gate that opens.
Also known as: Gap Between Worlds, The Gap, The Dimensional Gap, Between Worlds