The enigmatic being known as Dark Lantern seemed strangely familiar to those closely acquainted with the legacy of the Green Lantern Corps when he first made his presence known on Earth. He was created by the remaining Green Lanterns who had lost their rings when Hal Jordan went mad. They tapped into arcane forces and based on the unusual nature of the Bolovax Vik afterlife, they converted the soul of Kilowog into the Dark Lantern in order to send him after Jordan.
This is what wikipedia says, but I'm not sure thats quite the whole story. 😕