Read beyond this point at your own risk!
On Oa, Scar looks through the Book of the Black. She has been alive for billions of years, but has not died like other things have. Like the rest of the Guardians of the Universe, she knows that if the Emotional Electromagnetic Spectrum is harnessed, it will herald the Blackest Night, a darkness that will consume the entire universe and all light and life. But unlike the other Guardians, she knows the name of the darkness. And she worships it.
In Coast City, William Hand (aka Black Hand) lies in a open grave surrounded by rotting corpses when he hears a mysterious voice he refers to as death calling his name. While awaiting instructions, he reminisces about his life and how he's heard death calling his name as long as he can remember.
Hand's father was a mortician in Coast City. When he was little, he obsessed about his father's job even though his two brothers didn't. After killing and mounting the family dog, Hand is sent to a psychologist where he begins to develop a false identity that made him simply the black sheep of the family. This worked for a while...until his encounter with Atrocitus during his battle with Hal Jordan and Sinestro . Atrocitus gave Hand the cosmic divining rod that he built to "absorb power - including the light from the Green Lanterns' rings."
Hand's obsession with destroying the Green Lantern grew from this. The light of the Green Lantern was so bright it hurt William, and he intended to destroy it. He fashioned a costume out of a body bag and assumed the identity of Black Hand to try to stop Hal Jordan. When Hal Jordan became Parallax, the obsession subsided. The light haunting him had faded to a mere spark. But when Jordan became The Spectre, they encountered each other again. This encounter eventually ended up costing him his right hand . Hand eventually got his hand back after meeting up with the Kroloteans . This gave him the ability to hear and touch death but also see it. He began having visions of all the dead supers in the world, including those who died and came back to life. The voice wants them all.
Hand eventually ends up back at his father's mortuary where he murders his entire family and then himself using the cosmic divining rod. Scar appears next to the corpse of Black Hand stating that the murder/suicide pleases the mysterious voice. She then vomits up the first black lantern ring and proclaims that Black Hand is the embodiment of the Black Lantern Corp (much the same as Parallax, Ion and The Predator). Black Hand is prepared to use his power to extinguish the light once and for all.
The Black Lantern Corp is born....