Little is known about Vicente Sixx before the horrific events of the Drop Site Massacre on Istvaan V, when the traitorous Warmaster Horus Lupercal dealt a crippling blow to the XIXth Legion and its allies from the Iron Hands and the Salamanders Legions. During this massacre, the Raven Guard's Apothecaries were a designated target of the Alpha Legion Headhunter squads and suffered heavily. By the time Commander Branne successfully exfiltrated the Raven Guard survivors, only seven Apothecaries were amongst their numbers. With merely fifteen years of experience, Vicente Sixx was the most senior surviving Apothecary, and thus promoted to Chief Apothecary while still on board the Avenger.