Zone of Darkness
The Zone of Darkness[1, 2], also called the Zone of Shadow or Field of Shadow, was the place where the Visorak hordes contained the Zivon. Kahgarak were able to open a gap in the Zone of Shadow with their Rhotuka spinners, allowing the Zivon to emerge. Kahgarak were also the only thing that could send the Zivon back, preventing the horde from being wiped out by the Zivon's appetite.
The Zivon lived in a dimension of perpetual darkness which could be tapped into only by the power of the elite Visorak.
Very little was known about the Zone of Darkness, other than that it could apparently be accessed by the Rhotuka spinners of Kahgarak and that it was the natural domain of the Zivon.