Gareon was the First Captain of the Blood Angels Chapter, when his Strike Cruiser, Flame of Baal, encountered the Space Hulk Corruption's Heart in 674.M40. When the Space Hulk was scanned it was discovered to be infested not only with Genestealers, but also a thriving Genestealer Cult. Worse yet, Corruption's Heart contained a mining ship that held several functioning transports and would reach a populated Imperial System in mere days. In order to prevent the Genestealer Cult from infecting the System's worlds, Gareon ordered two Terminator squads to board the Space Hulk and plant thermal charges next to the mining ship's reactor. It was hoped that the resulting explosion caused by the thermal charges would create a chain reaction that would completely destroy the Space Hulk. However, though the two squads were successful in boarding Corruption's Heart, it is not known if they succeeded in their mission.