'Mdama was by far the most successful former Covenant member to command a fleet and uncover Forerunner artifacts for his advantage. Jul's motivations stemmed from early in the post-war era, when he was captured by the Office of Naval Intelligence, and his wife was killed during fighting with Thel 'Vadam's forces on Sanghelios. After 'Mdama managed to escape from ONI's grasp, he found a fundamentalist group of Sangheili and proceeded to recruit them on his quest of revenge.
'Mdama and his forces then managed not only to build a formidable fleet of former Covenant vessels, but used the knowledge of the Forerunners he had collected to locate the Ur-Didact's shield world, Requiem. On Requiem, Jul 'Mdama was able to recover the Janus Key, a Forerunner device that could point the way to every Forerunner artifact in the galaxy. While he only made off with half of it, he also managed to kidnap Doctor Catherine Halsey and use her knowledge to help strengthen his fleet.
After Requiem, 'Mdama's forces used covert tactics to recover the second half of the Janus Key and traveled to the Absolute Record to try and open its secrets. Jul was nearly successful, but ultimately failed and lost the Janus Key. He then attempted to make a recovery and continue uncovering more Forerunner secrets, but was found and assassinated by Spartan-IV Fireteam Osiris on the planet of Kamchatka in October 2558.