Nathaniel Garro

Nathaniel Garro was Battle-Captain of the Death Guard Seventh Company, a Terran veteran who refused the betrayal at Isstvan and stole the Eisenstein out of Typhon's reach. He brought the first true warning of the Heresy to Terra and paid for it by never going home.

Malcador made him a Knight-Errant. He hunted traitors through the war, kept a quieter faith than the Lectitio wanted, and was sent toward Titan with the other chosen when the Emperor decided the next war would be against the Warp itself.

Barbarus was his Legion's world, not his. Terra was. Whether he still stands on Titan or only in the Grey Knights' origin stories, the flight of the Eisenstein is the deed that made the rest possible.