The Twisted

When the K'Thonim were cast out of Atlantica at the start of the The Great Darkening the dimensional energies used were so powerful that it tore holes between dimensions, cast the K'Thonim from this world, and often by accident as reality became momentarily unstable near the The Plekenergia fused life forms together creating monsters of all sorts.
The Twisted are the intelligent peoples of the world, either The Eforoi or innocent bystanders that happened to be too close to the energies involved.  They were blended with other life forms from simple lizards, birds, insects, sometimes more than one.  Many died, twisted beyond the capability of life to support.  Many lived lives of pain, grateful for death when it finally overtook them.  Those that lived and bore children passed that twisting on to them. 
The Twisted were often reviled, sometimes justly, for many of them were the Eforoi that had been the "whip hand" of the K'Thonim.  As time went on however, those children of the twisted who had nothing to do with the K'Thonim are still reviled.  Their monstrous appearance shifted with each generation.  The Twisted often bred with other Twisted, creating braided lines of lineage that had unknown results.  Sometimes a child of two twisted would hit the genetic jackpot and look like they were a normal member of one of the intelligent species, to which they in turn would interbreed with.  This introduced Twisted genetics into the general population as well.
Now, some 3500 years after the Great Darkening, there are few pure twisted left.  Often persecuted, they hide in little enclaves around the world in remote areas.  They can be found in remote mountain valleys, or islands, sometimes they are intentionally isolated in colonies where they get sent.  There are even rumors of an enclave of them in the sewers and labyrinthine tunnels beneath Lutetia itself!  Sometimes the twisted are still villainized, but only because of their monstrous appearance.
It happens occasionally that a child will be born with the twisted gene.  It can skip any number of generations before it appears.  Parents otherwise delighted to have a child born to them might do any number of things, including leave the child in the woods for the Gods to care for, as horrifying as it is, it is often still done.

"Of course I didn't marry the girl, I found out she had a brother that was one of the Twisted.  I don't want kids that could end up like that!"