During the early years of the Great Crusade in the late 30th Millennium, Calas Typhon hailed from the Death Guard Legion's toxic homeworld of Barbarus. Typhon possessed the blood of the mutant psyker warlords that had ruled the planet before being defeated by Mortarion, the Death Guard's Primarch, who had been exiled to Barbarus through the Warp from Terra by the Dark Gods. When the Emperor reclaimed His lost son Mortarion from the poisonous mists of Barbarus, and reunited him with the the superhuman warriors born from his gene-seed, Typhon was amongst those chosen to join their ranks. Such was his strength of mind and body that Mortarion soon favoured Typhon above all others, elevating him to the rank of First Captain of the Death Guard Legion.