Zatheron was a rich technology based dystopia. Everything was run on crystals with high electric energy. That grew out of the ground from the center core.
Over centuries of using the crystals, they eventually became dry and the core became cracked and tainted. The oxygen became a thick acidic fog. The animal and plant life died off. The fog eats away at our skin and corrodes bones.
The Council of Technology and Intelligence advised a way to save what remains of the human race, the creation of cyborgs. Half machine, half human a way to survive. The ones who volunteered could go out into the fog with no trouble, other could never go outside again.
Later the COTI and their researchers collected data, and found that Zatheron is one of many sub-worlds. They built portals, to let our scouts go to these other worlds, to find a suitable place for cultivation.