Greeghan is a Sargorn employee of Balem Abrasax; Greeghan is primarily based on the Jupiter Refinery, but is periodically dispatched on missions that take him elsewhere. When the Sargorn leader, Tskalikin, was executed for the repeated failure to kill Jupiter Jones, Greeghan was promoted and given his mission. His first task was kidnapping the Jones family to use as a bargaining chip. After doing so, he remained at the Jones house with Mr. Night in order to wait for Jupiter. After she accepted their offer, he transported her back to Balems palace and had the Jupiter storm gate closed so her allies couldn't follow.
He and the other Sargorns strapped the Jones family into harvesting machines in a hidden chamber below Balems throne room and awaited the order to either kill or release them. Before the decision could be made, Caine Wise blasted his way in and attacked them. He successfully saved Jupiter and killed the other Sargorns before Greeghan attacked him. After a long intense battle, Greeghan wound up blinded in one eye, had one of his wings broken and a spike driven through his tail. Angry and hurt, he moved in to make Caine pay for injuring him. As he did, he was tripped and thrown through an opening in the floor, which Cain then sealed on him, breaking his neck and killing him.