Labyrinth

The Labyrinth is the means by which various iterations of reality, known as 'Levels', can be accessed.

Quotes
“That’s what they call all the different worlds. All the different realities. They’re levels. Each level can be reached by going through the Labyrinth.” - Dez, the Darkness at the Edge of Town

"Readers of my work know that all of my books and stories are part of an interconnecting story they refer to as The Labyrinth Mythos. However, this mythos has been deliberately kept subtle, so that the books are accessible to new readers at any point." - Brian Keene