Diclonius are a mutated kind of humans, thought by some to be too dangerous, and by others to be the next evolutionary stage of the human kind. The most distinguishable feature they have are their strange ear like bones, located a little higher then the ear and resembling horns. Their other distinguishable feature is the many long invisible arms having incredible cutting capabilities.
And since they look different since the moment they are born, when the ear shaped bones are spotted the kids either get killed or sent to laboratories for research. And how can a sentient being locked up in a lab feel? That is exactly where they learn how to hate and kill (using their long invisible arms). A run away diclonius is easy to track down, since usually after them you can find pools of blood and chopped up to pieces human bodies.
Translated from bulgarian language by Shakdun