Ok, so here's a base for a lore idea...
In the year 2158, the world was locked heavily in World War III. Devastating weapons tore apart men, armies, cities, and even countries as they reshaped the planet. It was during this, that several of the warring factions stood together to develop a new type of weapon, one that would cause fear and separation. This was know as Project Genesis.
Project Genesis dove into a field of science never before seen in war, genetic engineering. It was a compound that, when released, caused human DNA to become weak, and copy the genetic material of any animal. To put it simply, it turned men into beasts.
Soon, Project Genesis had turned into a full-scale war machine, and just like the power of the atomic bomb, everyone had to have it. The bombs were dropped without care.
Soon, most of the world had become a blast zone, and the number of people who were infected by Project Genesis skyrocketed. Xenophobia had never been greater as militant leaders chose to take the offensive and purge what they thought as "evil" and "tainted". Their victims could only watch and tremble, as their bodies could do nothing to stop the slaughter.
Fortunately for those to be killed, not everyone thought the same way, and they rushed to find even the slightest cure as they watched their friends lose their minds and bodies to the local wilderness.
Eventually, by referring to Project Genesis as a guide, scientists created a formula that would mutate the original compound of Project Genesis, converting the human DNA into a compatible form with the animal DNA. However, this was not a perfect solution...
Project Genesis proved irreversible, and those infected kept some animal traits. From fur, to ears, to muzzles, to tails, to the legs, the variation was wide, and that was only the majority. A minority of those changed mutated in different ways, from growing a human-like torso to only regaining their human minds and memories. A new race had been created, the "Creatura Populi".
All was good, until war fell once again. Humanity fought over whether to destroy the Creatura Populi, or to protect the life they had created from themselves. They knew these "beasts" were human beings once, but they didn't care as to what they were in the past, only to what they are now.
In the end, humanity wiped itself off the face of the Earth, but not before drastically changing it. Most of the technology and knowledge was lost in the destruction caused by wars, leaving the Creatura Populi to fend for themselves. It was not long, however, before they reformed one of the greatest achievements of mankind. Civilization.
They began exploring, regaining the knowledge that was once lost to them. They revived old technology to help survive, and explored the scarred Earth. They found many secrets that humanity had so easily overlooked, from basic sciences to a mystical presence that would allow them to eventually learn to cast magicks.
With each new explorer came old knowledge from the era of mankind, and soon, cities were rebuilt and technology improved. Some refused to abandon their ways for the new, and some chose different ways to advance. They broke into different factions, each with their own views and technology, and those factions still survive to this day.
Note, this is only an idea, it is not set in stone and may change.
