Alpharius
No such Primarch exists, please redirect yourself to the main page.
Original record
++Note that this record is kept solely for the Inquisition's records on heretical accounts and rumors. Nothing here is to be taken as truth, but more as myth and lies.++
Alpharius is the mysterious Primarch of the Alpha Legion. We don't have much information on him other than that Omegon, his bro, looks exactly like Alpharius, but we also don't know who Omegon and who Alpharius are, or which one is which. He was supposedly killed by Roboute Guilliman of the Ultramarines, but we may never exactly know if he killed Alpharius or Omegon, since the 2 looks strikingly the same. For all we know the entire Alpha legion is Alpharius and Omegon. Hell, they're so secretive they probably betrayed the Imperium to help the Imperium, which helped Chaos beat down the Imperium, which actually helps the Imperium kick Failbaddon's ass. He could probably be the one that's making Abaddon fail so much.
But what the fuck, we don't know.
tl;dr Alpharius is like Anonymous. There's over 3 billion of him and everyone is Alpharius. It's even worse than Spartacus.