Dreamscape

The Dreamscape is an extension of the known reality, which is believed to exist outside the three dimensions of the Material. The Dreamscape largely does not work in alignment with our world's natural laws. Rather, it is said to be a realm of madness and things incomprehensible.

Alright... Think of a sheet of parchment, laid flat. Now imagine ingrained into that parchment creatures, like drawings, except with the power of movement and thought and communication. These creatures may interact with one another, as well as with other objects on the parchment. To them, the sheet is their whole world. However, we know that beyond it, there is a whole reality, which we call the Material, though really it's just the one we're familiar with. To them, it is incomprehensible. They can only imagine life in two dimensions, so even the idea of something extending in a direction they can't perceive would be quite confusing and frightening. If you have not guessed it, this is an analogy in which we are the parchment creatures, and the Dreamscape is all that lies beyond our humble little sheet. Except there's one difference. This metaphorical race of paper-dwellers can't comprehend things that are outside of their two-dimensional plane. We, however, are blessed, or I should rather say cursed, with what some call the Mind's Eye, the gift of seeing into the Dreamscape.
Truthfully, even of our own reality we know pitifully little. It is a testament to our suicidal curiosity as a race that we continue trying to look beyond it.

Gant ond Zarle, Diviner

The Dreamscape is said to stretch infinitely in all directions, and possess such a great palette of wonders (and terrors) that anything one can and can't imagine might be found someplace in it. Many attempts have been made to describe and categorize the things that lie beyond the Material, but the further scholars went in such pursuit, the more difficult it became. There are well-supported hypotheses of living creatures inhabiting other parts of the Dreamscape. Very few of these "creatures", if one may even call them such, can cross into the Material, or influence it. The most well-documented such beings, and certainly the most frightening, are the Elders. Their reach is thought to extend across massive parts of the Dreamscape, and reach into and beyond the Material. However, the extent of, and the way through which the Elders meddle in the Material realm is concerningly poorly documented. What is well documented is the colossal danger of peeking into the Dreamscape. The mortal mind has the capacity to perceive into the Dreamscape, but hardly has the potential to process the likeness of other realms. Most points in the Dreamscape are relatively harmless to the mind. However, every so often, a "visitor" might encounter things beyond the capabilities of the human brain. Such things are most commonly products of the Elders' influence, and are known as the Seven Madnesses.