The Argo was a starship owned and operated by House Castana and in service to the Ultramarines legion at the beginning of the Horus Heresy. Her keel was laid down in the shipyards of Calth and served for one hundred fifty-six years before her destruction[1a].
The ship experienced a severe combination of Warp Storms which, combined with a lack of necessary maintenance, breached the vessel's Gellar fields; the subsequent daemonic incursion killed all hands except Astropath Kai Zulane and Navigator Roxanne Castana. Thanks to the assistance of the Emperor, the ship translated back into normal space before being completely destroyed. House Castana wrote off the hull as a total loss.