Generations ago The Glowing Sun shined down upon the world and the world was changed forever. Humanity hid deep within the earth, in what are now called Chrysalis trying to escape destruction. Some were lucky, others not so much.
They say your great-grandparents or so were the ones who were there, though very few of that age have survived to this day. The radiation sickness took many and those that did not mutate could not survive. What genes kept people alive were passed on and each generation has become a little stronger though a little more unusual. People can do things they've never done before and more things are found out every day. Of course, it wasn't just the humans, all creatures have had to adapt to this new way of life.
Many of the old ways have been lost, taken out in the blasts, secrets dying upon the lips of those who did not share. With no transmitters active there is no radio, no internet, no way to connect with the wider world. This is a time of having to learn, having to grow and having to start again.
In a bid to survive better a group of like minded mutants stuck together and decided to come out their chrysalis shells and make a place to call home. Using salvaged materials homes were slowly erected, rudimentary fences around animals became the first farms, non-poisonous plants were collected and their seeds strewn into the ground. Thus was Chimera born.