In the near future, many groundbreaking technological advancements were made, their utility fueled the flames of war, resulting in the loss of billions of innocent human lives. The upper echelons of human society tussled both openly and in the dark, their greed getting the best of them. For a time, there was momentary peace, people lived happily once again, reaping the benefits of the technology that they had ruthlessly turned against one another. It was a moment of respite, because exactly four years after that calm and prosperity, a new weapon was commissioned... a biological weapon.
There was little known about the superweapon, but many of people felt its effects. It changed their daily lives. The biological weapon was said to have been originally intended to instantly terminate an affected individual(s), and it did so... for a time. Us humans are extremely adaptable, we are able to learn from hurdles as well as emerge stronger from them. The same can be said for our genetic code, it adapted to the properties of the biological weapon and absorbed them. A weapon with the potential to eradicate all of humanity instead served to strengthen it.
When their DNAs were reprogrammed... they changed. Some humans weren't so human anymore. They resembled hideous beasts, gained unnatural abilities, experienced fits of delirium, displayed extreme hate for their 'inferior' cousins, and in the worst cases, were diagnosed with schizophrenia.
But there were humans that evolved differently from those who failed to completely assimilate the properties of the latent biological weapon, they were humanity's heroes. They were the Evolved.
As a superior caste when compared to the rest of humanity, the responsibility of dealing with their counterpart, the Abnormals, was placed on their shoulders. The Evolved fought valiantly alongside the normies, but they didn't quite manage to entirely contain all of the genetic aberrations.
The Abnormals continuously waged war against the Evolved and the Inferiors, resulting in their recurring defeat. They devised another biological weapon capable of countering the effects of the previous iteration, but the Evolved proved to be too strong, so the Abnormals commenced a tactical retreat, lurking in the shadows of the underworld and secret societies where they gradually amassed power and prepared for the next big war that would surely end in their victory.
With no common enemy left to oppose, the Evolved turned against the normies and enforced the New Order - a dark one. The normies were not mindlessly slaughtered, but instead relegated to the Lower Caste, while the Evolved were regraded as a superior specie known as the Higher Caste.