Atrocitus, originally known as Atros, was an alien native to the planet Ryut in Space Sector 0666. Countless years ago, by the time he reached adulthood, he had worked to become a psychologist and was married with his wife who had a young daughter. Their peaceful life came to an end when the renegade Oan Krona induced a programming malfunction in the Manhunters. This led to them exterminating all life in Space Sector 666 bringing about the devastating period known as the Massacre of Sector 666. Atros's homeworld was ravaged in this time and he saw his wife as well as his child ruthlessly incinerated by the android Manhunters which left Atrocitus as one of the few survivors. In fact, Atros became one of only five beings in the entire sector to escape death. He and the other four survivors formed a terrorist cabal known as the Five Inversions, bent on the destruction of the Guardians of the Universe and all who served them, and with Atrocitus serving as their leader. The Five Inversions performed a ritual which allowed them to peer into the future and discover the prophecy of the Blackest Night, which decreed that all life in the universe would end. They ruled a massive domain known as the Empire of Tears, until the Guardians of the Universe defeated the Five Inversions and imprisoned them on their capital, Ysmault.
After Abin Sur arrives trying to locate survivors of a crash, he went to the imprisoned demons and asks for their assistance. Atrocitus refuses to help him, but his comrade Qull freely offered to answer three questions: the location of the survivors, the fate of Abin Sur, and the prophecy of the Blackest Night. Sur told this to the Guardians of the Universe, in turn kept the Five Inversions on Ysmault instead of transfering them to Oan sciencells. Following this, Sur began to make periodic visits to Ysmault, to learn how to prevent the Blackest Night. Sur even went so far as to free Atrocitus from his imprisonment so he could lead the Green Lantern to Earth, the birthplace of "the black" that would end the universe. Caged in Sur's starship, Atrocitus instilled fear in Sur, allowing the yellow impurity to seep into his willpower constructs and weakening them enough to escape. After slashing the Green Lantern in the chest, mortally wounding him , Atrocitus jumped from a point high Earth's atmosphere to escape Sur's failing ship.
Atrocitus continued his violent rampage on the planet Earth. After killing an unspecified number of Air Force troopers, Atrocitus recited an oath that will possibly become the battle cry of the Red Lanterns and performed a ritual which gives him the name of the herald of the Blackest Night: William Hand. Atrocitus created a device using gun parts which acted as a cosmic divining rod, and used it to lead him to Hand (the device eventually became Hand's criminal weapon). Once he tracked down the human who, it is said, will play a prominent role in the coming of the Blackest Night, he attacked, and planned to take Hand's innards back to Ysmault. Before his plan proceeded, however, Sinestro and rookie Green Lantern Hal Jordan intercepted him, spiriting William Hand to safety. Atrocitus used his newly-constructed device to sap the power from their rings, leaving them with only their wits to defend them before the master of the Five Inversions. Sinestro is able to restore their rings' powers through his power battery, but Atrocitus still has the upper hand. Just as he is about to crush Sinestro with a power shovel, Hal uses his ring to blow up the yellow vehicle, suprising Atrocitus greatly, as he believes Green Lantern Rings do not work on yellow. Defeated, Atrocitus is contained by Sinestro, and taken to Oa. Later after Sinestro dropped Atrocitus back on Ysmault, Atrocitus and the other Inversions imparted a prophecy of the eventual rebellion of Sinestro's homeworld of Korugar. Sinestro didn't believe his lies and told him unlike Abin Sur he would not fall to fear.