Prior to that, he served as a Sergeant under the Ninth Order's previous Captain Alajos, as the Horus Heresy raged. Tragan was among the Dark Angels that took part in the Thramas Crusade, where their Legion clashed with the Night Lords. As the war with the Traitors wore on, the Ninth Order would join their Primarch Lion El'Jonson in traveling to the Dead World of Tsagualsa to meet his brother Konrad Curze, and finally put an end to their bitter conflict. When the Lion met with the Night Haunter, however, he left the Ninth Order aboard the small fleet that traveled with him and took only Captain Alajos and the Ninth's Paladin, Corswain to Tsagualsa's surface. The Ninth Order did not stay inactive for long, though, as Captain Alajos soon gave the order to deploy to Tsagualsa after the Primarchs came to blows. Alajos and Corwain also began battling the Night Lords Sevatar and Shang and it would be several minutes before the Ninth could reach the surface. Mayhem greeted them as they arrived, as both Primarchs had been severely wounded in their battle, while Captain Alajos was dead at Sevatar's hands and Corswain lay wounded after having attacked the Night Haunter to save the life of the Lion. Tragan immediately helped Corswain to his feet, as reinforcements from the Night Lords also arrived and both sides quickly pulled their wounded Primarchs aboard Thunderhawks and departed from Tsagualsa. After the Lion's fleet rejoined the rest of his Legion fighting in the Crusade, Tragan was chosen to take Alajos's place as Captain of the Ninth Order.