Karna-Kar was once a black dragon of the maelstrom age.
Karna-Kar was created by a powerful spell committed by the Dargean, a banishment that sent the chromatic dragons to neighbouring planes of existence. Iris Iknar was formed in the Feywild combining all colours but black. Karna-Kar could not be sent to a plane so vibrant, so was instead bound to the Shadowfell. There they suffered a lonely existence, where they evolved, adapted, and ultimately changed into a void of pure suffering.