Omegon
The twin brother of Alpharius; collectively, they are the Primarchs of the Alpha Legion. People know less about this guy than they do about Alpharius, so that's pretty much less than jack squat. In fact, people know so little about this guy and his brother that it isn't even known if they are one person or two. This is leveraged by the fact that everyone is either one of these guys or the other, including themselves.
If you don't know anybody who is secretly Alpharius or Omegon, you probably are him (or the other one (or both (or neither(or all at the same time)))).
...
Fucking samefag.
He was the one who invented the tyranids. They are actually a fiendish distraction so that he can break into the imperial palace on terra and raise TEH EMPRA from the dead (which make sense since alpha legion's military doctrine is like a hydra, which its head could strike from multiple directions at once, and which could keep going even with the loss of a head, just like tyranids, that they would split into splinter fleets if their main fleet is destroyed, and would keep going from planets to planets to regain their health back to hive fleet strength).
Conspiracies within Conspiracies (as usual)
Consider the following evidence:
1. Alpharius/Omegon sided with Horus despite being explicitly told by The Cabal prior to the Heresy that if Horus won it would mean the end of the human race but the ultimate victory against Chaos. While if the Emperor won it would mean the decay and eventual death of the galaxy, but humanity survives.
- Catch 22 with two undesirable outcomes, but hey, the Alpha Legion has two Primarchs, go figure?
- By the time of Vulkan Lives, the Cabal have apparently written off their "Alpharius Gambit" as a failure, despite from all appearances that the Alpha Legion joined Horus just like they wanted.
2a. Omegon discretely plotted against Alpharius to destroy an Alpha Legion facility which was causing warp storms and preventing the White Scars from returning to Terra. If this facility was not destroyed the White Scars would not have been present during the final battle.
- One brother conspiring against the other? Just like the rest of the Horus Heresy. Just because they are twins it doesn't mean they are always of the same mindset
2b. When the White Scars did eventually leave the Chondax system, the Alpha Legion "fleet" (actually made up of several "fake" battlecruisers with no real teeth) arrived to hold them in position long enough to receive orders from Rogal Dorn to return to Terra. Mortarion has no idea what that was meant to achieve (the mission was apparently to give them misinformation about Prospero and con them into helping a different, non-toothless Alpha fleet to wipe out the Space Wolves) and comments that Alpharius will end up "throttling" himself with all his schemes. Given that the other fleet did its best to wipe out the Wolves, it suggests two Primarchs working to different goals.
3. Someone in the Alpha Legion saved Corax and the survivors of Istvaan from the World Eaters
- If Corax died, the Raven Guard would have been finished and out of the war for good (much like the Salamanders were) instead they went on to rebuild and rejoin the war towards the end and still have enough marines left over to split into successor chapters
4a. Despite the Alpha Legion stealing the ORIGINAL genetic template of the Primarchs, they handed false information to Horus which would never have resulted in anything useful.
4b. ... said stolen genetic information was never utilized by the Alpha Legion either, even after 10,000 years, even when they could have been producing "super" space marines!
- ... hey? aren't Grey Knights an "original" space marine chapter with NO known Primarch? with psychic powers? AND an unusual resistance to corruption? And supposedly improved genetic template?
- ... When Malacador's Knight-Errant arrived on Titan there were
already 1000 battle brothers waiting for them. If these battle brothers (or the gene-seed used to make them) had been taken from another legion, then the other legions would likely have knowledge of them. The loyalist remnants of the traitor legions were for the most part wiped out on Istvaan and there would not have been enough left to make a full chapter. So where did these battle brothers come from if the only original source had been stolen?there were not 1,000 battle brothers waiting for them, there were thousands of recruits and the resources to make a Chapter there. The 1,000 Marines are only made when Titan is placed in the Warp by itself and they all get trained. Also 7th edition Grey Knights Codex hints that it has traits that none of the Legions Gene-Seed has (such as making the purer/more resilient to Warp Corruption (read Castellan Crowe's entry)) which would mean that they are an entirely new strain of Gene-Seed.
5. The Alpha Legion's first victory in the Horus Heresy was claiming the Forgeworld of Paramar, which was left in such a state that Horus had to garrison the world with substantial forces earmarked for warzones elsewhere just to maintain control over it.
- When Horus called Alpharius out on this bullshit, the encrypted response was "The Devil is not Mocked" which is an oblique reference to a
pulp story from 1973 where some Nazis get eaten by Dracula who was secretly aiding the WW2 Alliesproverb (the full saying of which goes "When evil faces evil, the Devil is not mocked"); the moral being just because they're both evil doesn't mean they're on the same side, and that a major evil badass won't automatically consider a smaller, also evil upstart his equal.
6. Omegon kept a hidden suit of armour on board his battle barge in addition to his "normal" legionary armour, one which he had planned a hidden purpose for to "strike unexpectedly like a serpent". This other suit was plain and unadorned...
- ... unpainted power armour is grey, also it's what Malcador's Knight-Errant wore.
7. The first Grand Master of the Grey Knights was named "Janus"
- the Roman god with two faces of "beginnings & endings" ie: Alpha & Omega
Let's just pray to the Emperor that this is not all just coincidence
Which Alpha Legionaire Are You?
Black Library has an Alpha Legion quiz on their site. About half the answers seem to lead to Alpharius, and the other half lead to Omegon (fitting for the two Primarchs). If you get "I am Alpharius" for your result, there's a description of him that basically encompasses all answers (but does tellingly say "You are absolutely loyal to your legion") whereas Omegon's description says he answers to no one in pursuit of his mysterious goals and will kill anyone in the way... Actually, we kind of already knew that, but at least this confirms it.
| The Primarchs of the Space Marine Legions |
|---|
 Loyalist Corvus Corax - Ferrus Manus - Jaghatai Khan Leman Russ - Lion El'Jonson - Roboute Guilliman Rogal Dorn - Sanguinius - Vulkan |
 Traitor Alpharius/Omegon - Angron - Fulgrim Horus - Konrad Curze/Night Haunter - Lorgar Magnus the Red - Mortarion - Perturabo |