Evolution, Devolution, or Modification
Being a mutant in Auropia is illegal. It is impossible for mutant immigrants to legally enter Auropia, but many do illegally. The ambient radiation and toxic smogs in Auropia frequently leads to birth defects and occasionally powerful mutations. Children of Citizens that show significant mutations are not killed, but they are forced into dangerous civil or military service, but many people hide their children from the government and security screenings. In the past the government of Auropia genetically engineered soldiers, workers, and even explorers resistant to the toxins of Rath. These mutations are still alive and some are even breed together or live in insular communities created by the government or corporations to keep useful mutations alive.
The most notable strain of mutants is the Rangers. They are officially part of the military, but live in their own isolated community with very minimal contact with the population of Auropia in general. The reason these mutants are famous is that they are popularized in fiction and vids. They are the only force of Auropia that regularly operates not only in the world beneath but on Rath in general. They scour the lands of Rath for useful caches of lost materials, plants and minerals.