20 or 21 Primarchs (participating in the Great Crusade)?

Question

One of the foundation elements of Warhammer 40k lore is the idea that the Emperor created 20 Primarchs, who were snatched from Terra by a Chaos vortex and scattered around the galaxy.

This was published at least as early as 2002 in the Index Astartes.

Eventually, all 20 would be recovered, lead their own Space Marine legion and all would participate in the Great Crusade.

For the order of recovery, the Lexicanum is a good resource. Their order:

• I Lion El'Jonson The Lion 11
  
• III Fulgrim The Phoenician 5
  
• IV Perturabo The Lord of Iron 12
  
• V Jaghatai Khan The Great Khan, The Warhawk 15
  
• VI Leman Russ The Wolf King, The Great Wolf 2
  
• VII Rogal Dorn The Emperor's Champion, The Praetorian of Terra 7
  
• VIII Konrad Curze The Night Haunter, The Lord of the Night 16
  
• IX Sanguinius The Great Angel 10
  
• X Ferrus Manus The Gorgon 4
  
• XII Angron The Red Angel, The Lord of the Red Sands 17
  
• XIII Roboute Guilliman The Battle King, The Avenging Son 8
  
• XIV Mortarion The Death Lord, the Reaper of Men 13
  
• XV Magnus the Red The Crimson King, The Red Cyclops 9
  
• XVI Horus Lupercal The Warmaster, 1
  
• XVII Lorgar Aurelian The Urizen, The Golden One 14
  
• XVIII Vulkan The Lord of Drakes 6
  
• XIX Corvus Corax The Raven-Lord 18
  
• XX Alpharius Omegon The Last Primarch, The Lord of Serpents 20
  
• ** Note that while II and XI exist, records of II and XI were expunged from Imperial records.

The only other problem then is that Omegon appears to be a hook thrown in.

As I understand, the primarchs were snatched while still in their “incubation capsules” — their bio-engineering growth crèche; then Alpharius split into an identical twin while still gestating within his capsule.

Being as least coy as possible with numbers of souls versus numbers of bodies or cylinders, what is the canon answer to the number of primarchs? Is this whole deception of the reality of 21 canon, does canon count it as no deception because the twins exist as a single soul as if Omegon is some sort of slave-botted hack, or is Omegon technically even a Primarch?

20 or 21?

Answer 1

Alpharius Omegon is a primarch. They are one in two bodies:

Alpharius Omegon (also known as the Last Primarch or the Lord of Serpents) was one of the twenty Primarchs created by the Emperor in the earliest days of the Imperium, just after the end of the Age of Strife. Like the other Primarchs, he was supposedly scattered from Terra by the Gods of Chaos and placed on a far-away world in an attempt to prevent the coming of the Age of the Imperium. In truth Alpharius Omegon are twins known as Alpharius and Omegon respectively, though they describe themselves as one soul in two bodies.

From the Lexicanum article on Alpharius Omegon

Another way to look at it is as the Primarchs as generals and head of a Legion. There were 20 Legions and therefore 20 Primarchs with one being able to share his duties with his twin.

Answer 2

Officially primarch count: 18.

Total primarchs created (in body): 21.

Legions formed: 20.

This is one of the most important concepts when it comes to understanding the Alpha Legion. They are led by their primarch, Alpharius, who has a twin brother, Omegon. Alpharius and Omegon were known to frequently change places with one another. This is why the Primarch of the Alpha Legion is often referred to as Alpharius Omegon, as the two effectively exist as one person in two bodies. It is noted in Praetorian of Dorn, that when Alpharius was killed by Rogal Dorn, Omegon, half a galaxy away, was able to sense this, and subsequently adopted the persona of his brother for entirely.

This, when combined with the fact that Alpharius and Omegon were known to be smaller than the other primarchs, and that their gene stock produced space marines larger than most other legions, is the reason the phrase "I am Alpharius" is so commonly said by Alpha Legionaries.

In conclusion, there were 21 bodies of primarchs, 18 official primarchs, and 20 souls created. This is really based on your own interpretation. As I see it, there were only ever 20 primarchs, with Alpharius Omegon being one soul in two bodies with two consciousnesses.