The origins of the Plague Marines can be traced back to the early 31st Millennium. During the opening days of the Horus Heresy, Ignatius Grulgor was the Commander (Captain) of the Death Guard Legion's 2nd Grand Company. During the massacre of the Traitor Legions' Loyalists on Istvaan III that initiated the Heresy, Grulgor was posted on the Imperial frigate Eisenstein to kill the Loyalist Captain Nathaniel Garro and his hundred-strong company of Death Guard Astartes. Grulgor was initially killed in a firefight on the gun decks of the Eisenstein, after a stray Bolt Pistol shot released the Life-Eater virus that had been intended to be used against the Loyalist Astartes on Istvaan III. After the successful escape of the Eisenstein and the following trip through the Warp, the body of Grulgor w