What lies beyond Creation?

Jewish mythology has this concept of an 'unfinished corner' of Creation. I was introduced to it, like many other kids, through ghost stories. Older kids tried to scare me and my friends by telling us about the empty blanks of the far North, inhabited only by wicked spirits who just loved to gobble up little girls....

I re-encountered the myth as an adult in the book Tree of Souls by Howard Schwartz, then began to find references to it in other Jewish mythological works as well. He provides the text of the myth in the book sample on his website:

All of Creation had been completed except for the north corner of the world. God began
to create it, but left it unfinished, saying, “Whoever declares himself to be God, let him come and finish this corner, and then all shall know he is a god.” There, in that unfinished corner, demons, winds, earthquakes, and evil spirits dwell, and from there  they come forth to the world, as it is said, From the north shall disaster break loose (Jer. 1:14).
When the Sabbath departs, great bands of evil spirits set out from there and roam the world. Because of the cold north wind, the north was identified as the abode of evil spirits.This myth explains why—because that part of creation is unfinished. Here God makes a challenge to those who assert that they are divinities. The true test for a divinity is the ability to create a world. So God left one corner of the world unfinished, with the challenge that anyone who could finish it would indeed be a true god. Of course, the clear implication is that such a creation would be impossible.Rabbi Moshe Hayim Luzzatto offers a different perspective about unfinished creation:“God began Creation but left it unfinished so that man could eventually bring itto completion” (Adir ba-Marom).
The Kotzker Rebbe said of this unfinished corner of creation: “One little corner—God left one little corner in darkness so that we may hide in it!”
Sources: Pirkei de-Rabbi Eliezer 3 ; Midrash Konen in Beit ha-Midrash 2:30; Sefer ha- Zikhronot 1:7;
The Book of Jubilees 2:2; Zohar 1:14b; Siah Sarfei Kodesh; Or ha-Ganuz.

So, Creation was intentionally left 'unfinished' up North. What interests me is that things very much are stated to exist in this place- yet apparently because of their malicious nature they mark the very place as separate from the normal, 'finished' world. Is this an innate quality of evil things- that they detach their own worlds from those created without such evil?

I'm also interested in the challenge the unfinished corner represents. It's a pretty great power move on God's part- if you think you're so great, go turn this awful wasteland into a proper part of reality, then we'll talk. Sounds like an excuse for an adventure in a frozen hellscape to me!