Durak Rask was a Master of Ordnance within the Death Guard during the Great Crusade and Horus Heresy. A fanatical follower of Mortarion, whom he viewed as savior from his early youth on Barbarus, Rask's loyalty combined with his intelligence and national skills for siege warfare saw him rise to prominence within the legion. Such was his skill for siege-craft that he earned a rare commendation from Mortarion himself after the Siege of Valstpol, a battle which Rask himself lost his left eye and endured horrific scarring.
When Mortarion sided with Horus, Rask was among the first and loudest of his supporters. During the Battle of Isstvan III, Rask volunteered to lead a vanguard attack against loyalist Death Guard elements, and perished in the battle. He was succeeded in his role by Gremus Kalgaro.