Parallax is the living embodiment of fear, a demonic parasitic entity which would travel from world to world, causing entire societies to destroy themselves out of fear and paranoia.

The Guardians Of The Universe trapped Parallax in the Central Power Battery on Oa. This caused the color yellow's immunity to Green Lantern rings.

Parallax saw a "kink in the armor" in Hal Jordan, a way to escape. He caused Hal to begin do have doubts, to begin to fear things, and the premature graying of his temples. A series of events led to Hal becoming even weaker; Death and Return of Superman, and the destruction of Coast City, Hal's hometown.

Parallax drove Hal into madness, and when Hal entered the Central Power Battery, Parallax fused itself with Hal's soul.

When Hal Jordan sacrificed himself rekindling the sun, he became the [[Spectre:char:2361], and Parallax was still bound to him.

Almost a decade later, Coast City reappeared... but only the street signs, and one building; Hal Jordan's old home. At the same time, Kyle Rayner crashes a ship into Highway Hill, New Mexico, and mumbles to a pair of hikers, "It has a name..."

The Spirit of Vengeance (The Spectre) explained to Jordan the truth about Parallax, while simultaneously on the Moon, Rayner did so to Green Arrow. Rayner explains that he journeyed to the edge of the universe, and on the tenth planet from the star Pagallus, the inhabitants told him that Parallax was actually a yellow demonic parasitic entity that was born at the beginning of sentience, feeding on fear, creating terror in anything it came into contact with, and causing entire civilizations to destroy themselves out of paranoia. The Guardians imprisoned this creature within the Central Power Battery on Oa, using fear's opposite energy, willpower. Rayner explained that there is an emotional electromagnetic spectrum into which the collective willpower of the universe is collected by the Central Power Battery, and that green willpower is the most pure. Parallax had lain dormant for billions of years, his true nature covered up by the Guardians to prevent anyone from trying to free it, and thus, it had eventually come to be referred to as simply “the yellow impurity.” This was the reason why the rings were useless against the color yellow: Parallax weakened its power over the corresponding spectrum, and hence only someone capable of overcoming great fear could master the power ring. The Guardians, therefore, selected only such persons to become Green Lanterns.

The Justice League Of America and Justice Society Of America arrive in Coast City to attack Parallax, but the entity inhibits their efforts by causing them to feel fear. The Spirit of Vengeance, however, manages to overpower Parallax, and finally removes the parasite from Jordan’s soul. Needing a soul to inhabit, Parallax attacks Ganthet, while Jordan’s soul is pulled toward the light of the afterlife. Ganthet manages to guide Jordan’s soul back to his corporeal body on the Moon. His soul and thoughts finally clear for the first time in a long time, Jordan emerges from the coffin resurrected as a mortal human again, once again taking his place as a Green Lantern, the white portions of his hair even restored to their original brown. He and Sinestro engage in a fierce battle on the Moon, and across entire star systems. Eventually, Jordan forces the renegade back into the antimatter universe into which he was first banished. Jordan and Rayner then journey to Coast City, where they, along with John Stewart, Guy Gardner and Kilowog, free Ganthet from Parallax’s possession, and imprison the parasite back in the Central Power Battery on Oa.

It was in the central battery that Parallax stayed for the next year, until the events of the Sinestro Corps War. When Sinestro began his bid for power his first move was an assault on the citadel of the Guardians themselves, the planet Oa. During this initial assault many Lanterns fell, and Superman-Prime, as well as Hank Henshaw were released from the Sciencells. Yet these were not the only goals accomplished by Sinestro’s soldiers. They also managed to free Parallax and to booby-trap the Central Power Battery. He was not kept long without a host, as part of his own brand of vengeance Sinestro had broken Kyle Rayner, who would now serve as the new host for Parallax. It was after this that he was introduced to the Anti-Monitor, the guardian of the Sinestro Corps, to serve as one of his heralds. Parallax was able to use the trap the corps of Fear had set to capture the rest of the Earth Lanterns. Reaching through the Central Power Battery he drew John Stewart and Guy Gardner to Qward to be tortured. He also captured Hal Jordan. After first tormenting him with images of his father’s final moments, he then dragged him to Qward as well. He then proceeded to attack him, while berating him about having taken over Kyle and his capture of the other Earth Lanterns. Creating two constructs, one of Kyle in his first GL costume, and one of him in his second incarnation as Ion, he began tearing into Jordan. After a little while of beating him around, he allowed the rest of the Corps to attack him, until the Lost Lanterns intervened. Parallax had no intention of allowing this opportunity to finish what he’d started so long ago to escape him. He attacked Hal and the Lost Lanterns full force, managing to torment and kill Jack T. Chance before they escaped. It was then that Sinestro returned to Qward, and Parallax went with him into the tunnels to hunt down the Lanterns. They managed to corner the Hal and the other Earth lanterns, and while Sinestro dealt with Jordan, Parallax attacked Guy Gardner. He almost managed to kill the Lantern before the rest of the Last Lanterns arrived yet again, this time with Ion in tow, and managed to escape him again. It was then that Sinestro sent him to scout ahead in Coast City and prepare for the final assault. While all of this was going on Parallax was also dealing with Kyle Rayner. Trapped inside his own mind when Parallax took over his body, Kyle has been forced to watch him commit these heinous acts. While he had been fighting Hal Jordan he had tormented him about his lost loved one, Donna Troy, Jade, Alex, and his mother. Using the power of his mind Kyle attempted to fight back, but Parallax was stronger. He was able to crush his spirit, or so he thought, Kyle managed to find hope and the power to fight back just as events in reality happened. Parallax’s first stop was the home of Hal Jordan’s brother’s family. Just as he was about to attack his family, Jordan arrived and attacked him, dragging him out into the dessert and away from his family. Hal called out to Kyle, and managed to get through to him, but his power ring died just as he was about to save him. Parallax absorbed Hal as well, and now with both of them seemed more powerful than ever. John Stewart arrived just as this occurred, and was forced to face this new foe. John managed to hold him off until Guy arrived with a painting Kyle’s mother drew to help him snap out of it. Inside of Parallax Kyle and Hal together managed to work together and find the willpower to escape. Though Parallax was not defeated, while the lanterns celebrated he made his move to regain his prisoners. It was only with the timely intervention of former Guardians, Ganthet and Sayd, that he was denied his victory. The two Oans trapped him in the 4 individual power batteries of the Earth Lanterns. He is currently still trapped.