Alpharius

Alpharius was the Primarch of the Alpha Legion, the twentieth and final Legion created. Uniquely among the Primarchs, Alpharius had a twin—Omegon—whose existence was kept secret even from the Emperor. Both brothers were smaller than other Primarchs, able to pass as regular Astartes, which they used to confuse enemies and maintain plausible deniability. Armed with the Pale Spear, Alpharius was a master strategist who favored complex plans within plans, making the Alpha Legion's true allegiances in the Heresy maddeningly unclear.