Dithparu, or "Night Spirits", was the name given to an ancient group of non-corporeal beings who predated both the Organians and the Metrons. They had evolved from physical beings, but had long forgotten their original forms and names. These lifeforms were exiled by a group of their fellow beings, called the Brothers of Light, to the Well of Souls on an unnamed planet millennia prior to the 24th century, having been deemed to be "evil, darkness, the night side of their own souls."
While the dithparu were confined in an energy field, they were able to interact telepathically with the humanoid, pre-Hebitian culture living on the planet where they'd been exiled. They were able to influence these people, who came to see the dithparu as gods. In time, they were able to use their influence to selectively breed the humanoids, and create a bloodline that was genetically able to serve as the physical host for a single dithparu. For generations, these "Night Kings" ruled, with the leader of dithparu, Uramtali, transferring from the father to the son upon the king's death.
Approximately 6000 years prior to the 24th century, the dithparu became trapped after Prince Nartal, the heir to the Night King, abandoned the death ritual before Uramtali could possess his body, and when an attempt to possess the king's illegitimate son, Ishep, failed.