Omegon

Omegon was the Alpha Legion's deepest secret made flesh, the near-identical twin of Alpharius, a primarch whose very existence the XX Legion concealed from the rest of the Imperium. The two brothers ruled the Legion as one, sharing a single public identity so completely that outsiders knew only 'Alpharius,' never suspecting that two hands guided the hydra's coils. Where the brothers differed, they differed subtly, and the Legion's labyrinthine methods gave them endless room to act in concert or apart without ever revealing the truth of their duality.

Omegon commanded his own portion of the Legion's designs, and in the fragmentary accounts that survive of the Heresy, it is his role that hints most strongly at the ambiguity of the XX's true allegiance. Some suggest that Omegon harboured doubts about the course his Legion had chosen, that a part of the hydra worked quietly against the very rebellion it publicly served, pursuing an end that only the twins comprehended. Whether the brothers were divided in purpose or merely presenting yet another layer of misdirection is impossible to say, a fitting uncertainty for a primarch who spent his existence as the hidden head of a Legion built entirely upon secrets.