Aubrey Jason, as Jackal level commander, lead a retrieval mission of a Pyramid power core from its war machine, in Bakerville in 1959, after its battle with Honor Guard. He was eventually tracked down by the Silver Agent. By 1977 he was still in Pyramid. And was the agent from Chicago, who brought Jitterjack to Astro City for Joey Platypus's use during a series of mob wars. And this was when Royal Williams, recognized him as the trooper who had killed his parents. It was later revealed that Pyramid was really backing The Deacon's bid for power after he ignited the gang wars.
During the upheavals the Pyramid organization was going through in 1982, Jason was in line to become a member of the Theban Council as Lord Ibis. It was at this point that Charles Williams and Royal Williams, had finally caught up to him and were about to enact their revenge. Jason was saved momentarily as it was also the Rise of Kerresh the Devastator. Weakened by the force of power from the being, Jason had the tables turned and was about to kill the brothers, but another battle managed to separate the brothers from Jason. While the brothers did survive and get medical help, Jason watched from the shadows to let them know he was still alive and out there.
Over the next two years, he was constantly on the run from the Williams brothers as they chased him out of Marrakesh, Haiti, Oslo, upstate New York and in Burma, with the latter having been with E.N.G.I.N.E. operatives. Jason then made his way to San Diego, with the brothers still on his trail. By this point Jason was paranoid and not even sure if the two were still close, causing distractions and destruction just to cover his trail, in case they were after him. But this was just a stop on his way to Las Vegas to meet with Dr. Norton Ganss who Jason, had secretly been funneling money to for Ganss' various projects. And now Jason wanted real physical power.
The brothers were making their way towards Ganss' hideout, as well as Mirage, Hellhound and the Silver Agent battling Ganss' Dynamoids. Just as the brothers arrive, Ganss has transformed Jason, into a powerful being. He had the ability to read the Williams brothers minds and manipulate energy. After he started threatening them, the other heroes arrived with a bang causing a distraction. This allowed Charles and Royal to blast Dr. Ganss' machine, with the power transfer not complete and sent what was left of Jason into pain and amid the rubble. Though once they did find him, in his weakened state, a blast of energy rejuvenated his new body, though unstable, let Jason get away from the brothers, heroes and other authorities.
A few days later he did turn up, breaking into an E.A.G.L.E. facility at Tuscon, Arizona and stealing a piece of the Sekmeht Stone to help make him more powerful. He returned a few days later to the City Center section of Astro City at a former Pyramid base presumably, using the Liegemen as his fodder, he was becoming nigh powerful full of energy and being able to tap into other energies and peoples minds to soup up his power and start a new Pyramid under the moniker of Lord Sovereign. But the Williams brothers had tracked him down again and we're preparing their attack, when the Silver Agent appeared to them and explained that the power Lord Sovereign and the Pale Horseman were tapping into was from the rip in reality opened up two years earlier by the Point Man during the Kerresh wake.
The Williams brothers did their job and distracted Sovereign and the Pale Horseman entered the fray after noticing something draining his power. The battles ensued and it seemed like Sovereign was about to get away, but the Agent managed to close the rift and Jason and the Pale Horseman blinked out of our existence.
Near limitless energy power and absorption as well as flight. He also was able to mentally control weak minds near him to become his foot soldiers.