In the time after time ended, the surviving humans huddled together in man-made underground shelters they called 'churches'. Still clinging to the same divisive beliefs that prompted the final war amongst them, they strived to conform to one another out of pure ignorance and fear. Every man, woman, and child was separated and segregated according to race, creed, geographical origin, sexual preference, eye color, and disease suseptability. Conformity without question was the most imminent law.
Then came the last terrorist organization. A small group of survivors with one misanthropic vision: Complete Human Extinction. Unaffected by the polluted atmosphere, and unafraid of the human virtue of conformity, this group called for the genocide of the entire human race regardless of labelled race, religion, gender, age, or any other segragative quality. Their methods were vastly varied, as they spread plagues, incited riots, started wars, and collectively sought to precipitate natural disasters. They even experimented in genetically engineering predatory plant-life. All of their efforts were devastatingly successful. The time after time ended became a nightmare realm of chaos where human beings lived in constant fear of another terrorist attack.
This group of misanthropes thrived in that realm and became known to the world by it's effect on the human populace: Deterioration.
To this day, their attacks grow in violent brutality and frequency. There may be no hope for homo-sapiens left.