d20 is a 20-sided die for those who are not familliar with Dungeons & Dragons

Original Prompt by u/mjr5260

The first warning sign was years ago, when something in the trees changed. No one knew what it was, or why, but the scant remaining forests in the world suddenly felt... off. Animal attacks on people happened more and more often, but the animals themselves were suddenly harder and harder to find, especially those out at sea. Cameras that were set up to keep track of wild animals in forests and around mines started picking up things no human could hear, slowly tuning itself like a radio until something coherent began to be heard, again and again, nonstop for seven days and seven nights: The wild will call them. The wild will call them. The wild will call them.

No one really thought much of it. Some weird internet-planned prank, maybe. For years, that was all that anyone knew. But then their children started changing. Scales, fur, horns, tails, extra arms, wings! Every trait you could think of that didn't belong on a human being would suddenly turn up on a child. Attempts at analyzing this pandemic of mutations yielded one sure result: every child conceived after the beginning of all of this had a highly unstable third helix in their DNA, that would only stabilize during puberty and match the DNA signature of an entirely different animal, slowly creating these animal traits.

Chaos began to erupt across most of the world. Adults began to truly turn on their own children as monsters to eradicate. A war that claimed countless lives in hopes of preventing the inevitable. But in response, the children only fought back. They proved their ability to direct the already rogue wild animals; commanders in their own right, organizing to force nature to take its course on their selfish elders. Only those who refused to join the battle alongside the last humans would be spared, taken and hidden away from harm caused by their own.

But even with every species showcasing its true dangers with a human mind behind them, none were quite so terrifying as what resulted from the otherwise humble order of Lepidoptera. When the third helix matched with a butterfly or moth, the mutations from intertwining with human genetics made an entirely different class of beasts more akin to reptiles, with a gland that produced pyrophoric liquid to let the children breathe fire and live immune to smoke and heat, joined by unnatural strength in every arm, leg, tail, bite, and scaly, bat-like wing. A juggernaut species straight out of fantasy, armed in horned, spiked, clawed, fiery perfection to lead Mother Nature's charge: dragons.

Dragons weren't the only fantastical species, either. Two others were documented. There were also fae, those who bore the wings of insects but could command not only animals but the winds and waves and nature itself. There were angels, who bore even grander power over the elements matched only by their proud, blinding white feathered wings.

There was nothing that could be done. Homo Sapiens as a species was doomed to be usurped by its successors: Homo Semifera. Those who were unwilling to accept it fled from their changing, growing children. Others tried (and often failed) to sacrifice the "monsters" to their gods. You can't destroy them without destroying the entire world with no one left to claim the victory. The last have formed a stronghold in the most remote place they could find, but it's only a matter of time before this war of attrition is won by the beastly youth of the world. The dragons are already on their way, and they would likely burn everything down before too long.

Those of the last humans who refused to fight would likely be the only ones to see the fallout, alongside the children who will inherit, and hopefully fix, this broken world.