Jast was the Force Leader of the Outer Rim Defensive Battalion and was chosen to be part of the Cult of Skaro along with Dalek Thay, Dalek Caan and their leader, Dalek Sec. The purpose of the cult was to "think as the enemy thinks" and come up with novel and unorthodox methods of furthering the Dalek's cause during and after the Last Great Time War. It was their leader, Dalek Sec, who began using their initiative to defeat enemies. (PROSE: Birth of a Legend) During the Time War the cult escaped the carnage by hiding between realities in a Void ship, along with the Genesis Ark, which contained an army of imprisoned Daleks. (TV: Doomsday)