In "", it is revealed that Jordan was under the influence of a creature known as Parallax when he turned renegade. Parallax was a creature of pure fear that had been imprisoned in the Central Power Battery by the Guardians of the Universe in the distant past. Imprisonment had rendered the creature dormant and it was eventually forgotten, becoming known merely as the "yellow impurity" in the power rings. Sinestro was able to wake Parallax and encourage it to seek out Hal Jordan as a host. Although Parallax had been trying to corrupt Jordan (via his ring) for some time, it was not until after the destruction of Coast City that it was able to succeed. It took advantage of Jordan's weakened emotional state to lure him to Oa and cause him to attack anyone who stood in his way. After killing several Green Lanterns, Jordan finally entered the Central Power Battery and absorbed all the power, unwittingly freeing the Parallax entity and allowed it to graft onto his soul.