===Great Crusade===

It is believed that at first Vulkan did not become unified with his own Legion for some years after his rediscovery, instead staying alongside the Emperor under his tutelage and fighting by his side. When Vulkan was eventually reunited with his Legion, it was at the head of a fleet of 3,000 new recruits which saved his forces from a massive [[Ork]] horde.{{Fn|5}}

On the world of [[One-Five-Four Four]] Vulkan and his army came into contact with tribes of primitive humans living alongside [[Exodite]] Eldar. Surprisingly, the humans did not welcome the Imperial invaders. Vulkan was guided by a mysterious Remembrancer (later discovered to be a psychic projection of the Emperor) to a Webway Portal. After a vicious battle the Portal, Vulkan came across human tribals preparing to sacrifice a Dark Eldar woman. The Humans had learned to fear the [[Dark Eldar]] raiders, and sought to sacrifice her to ward off their return now that the Exodites had been defeated. Moreover, Vulkan realized that the Dark Eldar woman was from the raiding parties that terrorized Nocturne in his youth, and these humans were descendants of Nocturne captives liberated by the Eldar. Vulkan realized the Emperor had guided him here and understand that these humans would never accept the Imperium over their Eldar liberators, ordered the planet cleansed. He sought to erase any trace of Human-Xenos coexistence.{{Fn|13}}

===Horus Heresy===