Like the other Primarchs, Alpharius and his twin brother Omegon were transported from the Emperor's gene-lab beneath the Himalazian (Himalayan) Mountains of Terra through the Warp by the Chaos Gods and placed on a far-away world in an attempt to prevent the coming of the Age of the Imperium and the expansion of the ordered Imperium of Man across the Milky Way Galaxy. Alpharius Omegon was eventually rediscovered by the Primarch Horus and sent to meet his father the Emperor on Terra, who placed him (and secretly, his brother) in command of the XXth Legion, the so-called Alpha Legion, during the Great Crusade of the late 30th Millennium.