These mutated beings were the work of the exiled members of humanity who believe that the next step in evolution is not just through cyber enhancements but also through forced biological mutations. These beings have adapted to live in underground caves where they have experimented on each other to mutate and evolve to survive the highly toxic atmosphere. They call themselves the Chimeras having mixed their DNAs with various life forms they collected which once roamed the earth. These mutations gave them increased senses and strength. However, their source of energy is limited and extremely difficult to produce due to the difficult terrain and extreme weather on the surface. This forces the Chimeras to constantly attack the city of Corinth and steal whatever energy sources and technology they can to survive and to someday create their own utopia.
More info and story here: