Alpha Legion

The Alpha Legion's primarch was named Alpharius, and was actually one of the identical twin Primarchs Alpharius Omegon, two brilliant and secretive sons of the Emperor, one of whom was believed slain at the Battle of Pluto during the Horus Heresy by Rogal Dorn of the Imperial Fists and the other reportedly after the end of the Heresy by Roboute Guilliman, the primarch of the Ultramarines. Despite its seeming allegiance to Chaos, a closer scrutiny of the Alpha Legion's known history indicates that their seeming service to Chaos Undivided might actually be the greatest deception they have played upon the Imperium.