The Void
The Void is a place inaccessible to anything not from there. Our only way that we know its there is from the creatures that tell us about it. The Void is said to be a completely empty place, empty of everything, with creatures that are horrifying and some might bring the end of us if they so please. From testing, defense is not trivial, a good, but unreliable because of its users, are the Elements of Harmony, See "Elements of Harmony: A Reference Guide". From the descriptions given, it would drive any non-inhabitant insane.
“TWILIGHT!!” A small voice called out, “what are ya doin’ in here with tha lights out?!”
“Well, if you must know, I got this strange little book on my doorstep yesterday, and I intend to uncover its secrets.”