Era beginning/end
With little human interference, nature begins to reclaim what is rightfully its own, resulting in a revert of mankind's advancements.
As the Morose Affliction tears down society and takes many lives, the population drops to a low 700 million. The few that managed to survive had done so by having immunity, creating hasty vaccines, or by isolating from the rest of the world. With the population dwindling and most of Earth in scrambles, the era known as the Green Age had begun. This era marks the end of the Morose Affliction, and earns its name due to the downfall of man and its creations. Many sprawling cities and establishments are overtaken by nature, creating hauntingly beautiful "ghost cities" once abundant with people.
Society recedes into one run by tribes and clans, with disputes over resources and land being commonplace. Gunsmiths and others who've had experience handling a firearm have went extinct long ago, and as a result, melee weaponry becomes a standard mean of self defense.
During this time, the Mobile Purification Unit sees an increase of members as it boasts the survival of mankind as its own doing. An obvious falsehood, but lost souls with little to look up see the MPU as a beacon of hope. With the Morose Affliction effectively eradicated, a new leader oversees the faction's next move -- complete domination of the fallen continent of the Americas.