It was only later on after the war that there were people who began being able to combat mutants and withstand the toxic infection, each displaying unnatural releases of colored smoke from their nose and mouth.
Continuous studies on the phenomenon led to the foundation of "DIA" (or more commonly known, "Spirit Animal"): The self-discovery of one's spirit animal that would become an asset for them when combating mutants.
A person cannot decide what their DIA will be, and the results are not influenced by their natural personalities and traits.
On an average percentage, most people are able to discover it by the age of fifteen and on rare occasions, children below the age of ten.
Should a person fail to connect to their spirit animal when they are old enough, by government's law, they are not allowed on the field of battle against mutants, regardless of their skills.
When combating against a mutant without a gas mask, an individual will begin breathing out a colored smoke that aligns with their DIA. It protects them from the infection for a period of time (time varies between individuals) until they are able to get away from mutant air, or retrieve a gas mask.