Ascension to High Rock

We poisoned the Earth, and in response some of us mutated and others just continued to die. Now the "Evolved" live on the barren High Rock above the thick layer of brown smog that hides what's left of their more "Primordial" ancestors. It is in fact the "Primordial" us that poisoned the Earth. We aren't Evolved enough to drink the water, or eat the food, so naturally we depended on the more Evolved species to provide it.