Juskina Tull was a member of the High Lords of Terra and Speaker for the Chartist Captains in 544.M32 during the War of the Beast. Commanding over 90% of the Imperial Fleet, Tull's power potentially eclipsed that of Lord High Admiral of the Imperial Navy Lansung.
During the war she would cynically try to exploit the disaster for her own gain, raising the prices of passage and transportation between Segmentums despite a flood of refugees. Later, following the appearance of an Ork Attack Moon over Terra, Tull was able to oust Lansung from his position of power with the aid of Ecclesiarch Mesring.
Now ascendant, Tull condemned the Imperial Navy and organized a mass offensive against the Ork planetoid by civilian volunteers and Merchant Fleet vessels known as the Proletarian Crusade. Thanks to a lack of real military resources, poor planning, and Tull's complete lack of military experience the Crusade was a complete disaster, ensuring the Speaker's ascendancy on the Senatorum was brief. In the aftermath of the disaster, Tull fell into a sort of broken fugue state, appearing disheveled and saying nothing at subsequent High Lords meetings. She temporarily snapped out of her shock when she supported Koorland and the Inquisition in removing Lord Commander Udin Macht Udo from power.
In the aftermath of the war, Tull was among the High Lords killed by Grand Master of Assassins Drakan Vangorich in his coup known as the The Beheading. Her death was achieved by having her handmaiden Anastay, in truth an agent of Vangorich, goad her into suicide. Tull, broken and guilty due to the failure of the Proletarian Crusade, quickly gave in and shot herself.