Nightmares are caused by demons. Or magica. Sometimes angels, probably. I am certain nobody had nightmares in Pre-(H)istory.
Although relatively few demons come to the "surface", they very frequently show up in dreams. Many times our dream space seems to hold elements that seem prophetic, although maybe not in useful ways.
Why do we not simply sleep without thought? It sometimes happens that way, but so often we are taken on flights of fancy!
I believe that with the proper runic protections, we could sleep much more soundly, and avoid any interference in our most vulnerable times...
Please. I need no more dreams.
-Writings on Dream entanglement by the witch Nicky