Is poison purple or green?

"We felt we had grown up, and it was time to move on. We left god behind and in turn he left us to our world. While he was gone, there was a knock on the door."

One day without any warning, we were visited by creatures from another world. They hadn't traveled across the stars, but across dimensions. The first to arrive was the daezra, a people driven by a mix of starvation and religious fanatacism. They consume ashes, and were excited at the prospect of burning our world to feed upon it. The second were the naraxas, meek but clever. After a war in their own world they were forced out to look for a new home and found us.

They were not prepared for our defenses, our militaries were enough to drive even the zealous daezra back. Bullets and bombs were alien to them, and the destructive power we could dispense proved too much. But unfortunately, they brought something far worse with them. The exelca silvarum, also known simply as "The Plague". Exelca silvarum spread rapidly, it was airborne and very sturdy, as long as the portal to the daezra remained open it could not be contained. It caused cancerous growth in almost anything it infected, in our panic we decided to utilize nuclear weapons to try and end the daezra threat before we would be wiped out by this infection. We forced ourselves into quarantine, hiding from both the plague and the radiation while the military tried to deal with the daezra who had begun to run wild as our populations fell to the sickness.

Exelca silvarum killed 80% of the human population and many species of plants and wildlife. The invaders themselves were hardly a threat compared to what they unknowingly brought with them. What survived the plague developed strange characteristics. Combined with the radioactive fallout of our nuclear weapons many plants and animals mutated into new species entirely, including ourselves. We learned of our hidden powers thanks to the naraxas, and the very plague that killed us. Those that survived were stronger, their out of control cells could regenerate their bodies faster, and their psychic powers manifested.

The world itself has begun to reclaim all that we once built upon, within just a century the plants infected by exelca silvarum overtook anything it could touch. Our cities fall to ruin as the wild reclaims them, and only small pockets of human population manage to maintain any degree of technology. The daezra remain, and so too do the naraxas. The beasts who survived the plague have become monstrous, and our position on the food chain is challenged. The world is a harsh and dangerous place to survive, but slowly we try to reclaim what was always ours.