Alpharius / Omegon

Origin & Rediscovery

The Alpha Legion claim — and almost everything about them is something the Alpha Legion claim, which is exactly why almost nothing about them is settled — that Alpharius was the last primarch recovered, that the Emperor never knew there were two of them, and that Omegon walked the Legion at his brother's side from the day they emerged from the gestation pods. Two primarchs in identical armour, identical insignia, identical helm. Switching at need. Sharing the name.

No other primarch ever saw both of them at the same time. None of them quite believed it when Horus first explained — and even Horus only knew because Alpharius (or possibly Omegon) had elected, on a quiet evening, to show him.

Which was, of course, the point. The XX Legion did not exist as twenty thousand individuals. The XX Legion existed as one decision split in two, repeated downwards until every operative could wear the primarch's name without anyone — including the operative — quite knowing which version was true.

Method

The Alpha Legion fought by indirection. Where Russ stormed and Dorn besieged, the XX Legion infiltrated, suborned, manipulated, and quietly arranged for the enemy's own forces to do the necessary killing — sometimes years before the official engagement, sometimes during, sometimes after. Every operative wore the name Alpharius. A deliberate erasure of individual identity that made the Legion functionally impossible to decapitate: kill an Alpharius and another stepped into the role, with no break in the operational continuity, because the role itself was the unit of organisation rather than the man.

They were also strange. Socially awkward in council, frequently absent from inter-Legion gatherings without explanation, given to elaborate practical jokes that nobody else found funny. Other primarchs treated them as junior. Other primarchs were possibly being managed.

I am Alpharius. This is our finest hour.

— Alpha Legion catechism

The Cabal

According to fragmentary, contested, possibly-fabricated sources, the twins were contacted at some point during the Crusade by the Cabal — a xenos collective that had spent uncounted millennia modelling the warp, the Imperium, and the eventual shape of the war between them. The Cabal's argument to Alpharius, reconstructed from a single secondhand account, was that Chaos drew its strength from humanity's growth as a galactic species; that the only way to deny Chaos a final victory was to end humanity before it grew into the fuel-source the Dark Powers needed; and that the cleanest end was for Horus to win the Heresy, fast.

Alpharius believed enough of this to join Horus. Whether he believed all of it. Whether the Cabal was lying. Whether the Cabal existed at all. Whether the Alpha Legion was secretly working towards the Cabal's plan, secretly working against it, or — and this is the version some Inquisitorial analysts find most credible — both, depending on which of the twins one happened to be intercepting. These are the central, unanswered questions of the XX Legion.

The Heresy & Pluto

Alpha Legion operations during the Heresy were ambiguous in ways no other Legion's were. Some operations genuinely served Horus and the Traitor cause. Others appeared, in retrospect, to have crippled traitor forces in ways that suspiciously benefited the loyalists. Asset positions were leaked to both sides. Couriers were intercepted by both sides. Entire planetary compliance plans were executed and then quietly reversed by the same cells.

At the Battle of Pluto, Rogal Dorn — patient, literal, finally and entirely done with the XX Legion's ambiguity — caught Alpharius in person. They duelled. Dorn killed him. The body, when retrieved, was confirmed to be a primarch.

Dorn never quite explained the duel. Omegon's movements after Pluto are unknown. He may have survived. He may not have. He may, given everything else about the Alpha Legion, not be a single person at all.

Legacy

The Alpha Legion in M42 are still active and still impossible to read. They appear on both sides of conflicts, sometimes simultaneously, sometimes against each other. Imperial intelligence treats every captured Alpha Legionnaire as a deliberate plant; every defector as a sleeper; every confession as a deception three levels deep. Every member, asked, claims to be Alpharius. Some of them probably are.

They may be the only Chaos Legion still secretly trying to win the war for the Emperor. They may be the most thoroughly compromised. They may be both. Both possibilities are consistent with everything observed. The only thing certain is that ten thousand years after Pluto, an organisation that should not have survived its primarch is still operating with apparent strategic intent. Someone is still making the calls. Someone is still wearing the helm.

You will never know if we were always loyal. That is the point.

— Attributed Alpha Legion communique, captured M41