Baneling

Found generally during the Great War, the Baneling was a mutant created artificially by the magic of the Dark Gods. Combining dark magic with human and esper blood, the Banelings were born. They were made with no sanity and no reasoning except to obey the commands of their masters, the Dark Gods. And because of their unique blend of blood, Banelings were imbued with special powers. First and foremost, they blend in with shadows, making themselves invisible where there is any shade to be found. They are also seemingly invisible, unable to be touched by anything that could not harm a shadow. Second, they can make themselves generally untraceable even in broad daylight. When a normal pair of eyes would normally spot them, they would instead slide right over a Baneling, unable to focus or even really notice its existance.

Banelings were used widely as assassins during the Great War, and were thoroughly effective. So effective that to this day, you can find that any major Grand Army station is well lit beyond necessity, in an attempt to prevent any shadows.

Baneling were hunted nearly to extinction at the end of the Great War. Few, if any, still live.