Torghun Khan was a member of the White Scars during the Great Crusade and Horus Heresy. Born Haren Svensellen in Terra's Scandinavian region, Sven dreamed of joining the Luna Wolves and had a great reverence for their Primarch, Horus. However, due to his under-performance as an Aspirant Sven was reassigned to an under-strength legion, and his dreams of glory in Horus' Legion were shattered when he found himself in the White Scars instead. While he eventually accepted his place in the White Scars, and took a new name - Torghun - from his Primarch's homeworld of Chogoris, he never lost his admiration for Horus.
During the Great Crusade Torghun became a close comrade to Shiban Khan and rose to become Khan of the Brotherhood of the Moon. However, Torghun also became a member of a warrior lodge society within the Legion, a fraternity whose predominantly Terran-born members wished to ally with the Warmaster Horus. Torghun, along with his commander Hasik Noyan-Khan, planned to take control of the White Scars fleet while their Primarch Jaghatai Khan was on Prospero and bring the V Legion to Horus' side. The conspiracy was uncovered by Shiban, who led his Brotherhood of the Storm aboard the Swordstorm. On orders of Hasik, Torghun and his forces battled Shiban's boarding party. Torghun was reluctant through the entire ordeal but he genuinely believed that siding with Horus was the only way to preserve the Imperium. However when Jaghatai made it back to his fleet Torghun, Hasik, and other pro-Horus conspirators Goghal Khan and Hibou Khan willingly surrendered themselves. Held as a prisoner by his own Legion thereafter, Torghun eventually joined the ranks of the Sagyar Mazan.
Four years after the events on Prospero, Torghun was one of the few remaining Sagyar Mazan and its highest-ranking survivor, leading near-suicidal raids against traitor forces without support from his own Legion. Torghun had embraced his sentence of atonement through death with honor, so that when Jaghatai Khan called for a rendezvous of the Legion at Dark Glass he answered the call despite the pleas of his subordinates to ignore it. After an acrimonious reunion with the bitter Shiban Khan, where his former brother branded him an eternal traitor, Torghun found his ultimate chance for atonement during the ensuing Battle of Catallus. Torghun led the remaining Sagyar Mazan aboard the abandoned Swordstorm in a feint designed to trap Mortarion aboard the doomed vessel and allow for his own Legion to escape into the Webway. After setting the Swordstorm's engine to overload, Torghun was slain by Mortarion himself just before the Primarch was barely able to escape.