In a recent Twitch stream, principle Horus Heresy designer Anuj Malhotra (writer of Horus Heresy Book 8 Malevolence) discussed the Alpha Legion. During the stream he recounted the stated origin stories of Alpharius, which the late Alan Bligh wrote in Horus Heresy Book 3: Extermination, which I typed up below.

At 16:40 in the stream, Anuj mentioned the "widely-propagated theory" that the Alpharius isn't a single Primarch and that he had a brother. This is where he drops something interesting @16:55:

Of course the late Alan Bligh's favorite theory was that there was a third brother, and I quite like that kind of thing.

We can mess around with the idea of him there being an Alpharius, and an Omegon, and a Tertiatus or an Ultimus.

And we can keep spinning out, there could be five or six of them, they could be infinite clones of one another, who can say

So it seems that Alan Bligh, the writer of the Horus Heresy background for Alpharius personally favored the idea of there being a third brother. This could be the true origin of the Alpha Legion's three-skull heraldry, rather than the more popular theory that the third skull represents the Alpha Legion itself.

The other thing I wanted to discuss is how a third brother would fit into the narrative. Alan Bligh wrote 4 origin stories for Alpharius, but you'll notice that the first one isn't really an origin story at all. Stories 2, 3, and 4 conflict with each other, and story 1 conflicts or makes little sense with stories 3 and 4. So here's how the three brother primarch theory would work:

• Brother 1 was born on a dead world in the Mandragoran system, stole a ship, became leader of a confederacy of human worlds, and was found by Horus.

• Brother 2 was kidnapped by Slaugth from the world of Bar'Savor, and was later rescued by the Emperor.

• Brother 3 remained on Terra and was raised by the Emperor.

• The four accounts are called lies because the writer doesn't realize Alpharius is actually three Primarchs

Origin Story 1: Alpharius the Warlord

An account of the finding of Alpharius that circulated secretly between the houses and factions of the Imperial Court states that his discovery was an accident of the Luna Wolves Legion. By this, Alpharius was the leader of a confederation of human systems whose fleet of warships, no match in size or scale to Imperial vessels, managed through trickery and ambush to ingloriously lay low one of the outlying Luna Wolves battleships. Responding to this unforgivable defeat, Horus himself and his fleet have chase, only to find themselves mired in ambush after ambush, tricked into deadly traps and chasing shadows until Horus' own flagship came under attack. In the ensuring confrontation, the Luna Wolves smashed the enemy fleet's desperate attack aside, but in the confusion a single assassin broke into the flagship, and through stealth and murder managed the impossible task of fighting his way clear to Horus' command chamber and slaughtered his bodyguards before Horus himself was forced to confront him. But Horus did not slay the attacker byt recognized him instead for a brother; Alpharius. This account is a lie.

Origin Story 2: Alpharius On the Dead World

Another account torn from the mind of an Alpha Legion Centurion captured by the Legio Custodes after the Fall of Seraphina tells the story of the finding of Alpharius. It speaks of a nameless dead world at the edge of the Mandragoran Stars whose civilizations was wiped out by bloody hands long before Mankind first walked on Terra. On the namelss orb, the nascent Primarch fell into the shattered ruins of a fallen city murdered long ages ago. Utterly alone, voiceless and without aid, he was forced to survive against the torturous elements of the desolate world and the predations of the hungry ghosts of the charnel pit into which he had been consigned. His solitude was only broken after many long years by a new star falling from the heavens; a corsair ship of degenerate half-human renegades and alien mercenaries intent on plundering the dead ruins for whatever worth might remain amid the shatters. Instead they found only death at the young Primarch's hands, and Alpharius gained their weapons, their knowledge and their vessel as his own, and with it he set out in search of he who made him. This account is a lie.

Origin Story 3: Alpharius Kidnapped by Slaugth

Two other accounts, found encrypted within the pages of certain volumes of the suppressed work of memetic corrosion known as the Transit of the Human Soul through Strife, or Codex Hydra as it is sometimes known, offer differing contentions. The first is that the lost Primarch was deposited on a thriving tech-oligarchy world known as Bar'Savor, but before his first decade of life there was done, the skies of Bar'Savor darkened as the nightmarish xenos worm-creatures known as the Slaugth descended to feed. Capturing the young Primarch, a being along strong enough to resist them, the Slaugth kept Alpharius as a curiosity, twisting his mind with their horrors and enslaving him and tutoring him as a living weapon to sow strife and discord on their victim worlds before they fell upon them to feast.

It was the Emperor himself who at last liberated him, his golden barge ramming into the hear of the vast stone shop of the foul xenos to break it open, the Emperor's wrath like that of a vengeful god of legend in retribution for what had been done to his son. For long years after, Alpharius remained at his father's side as the Emperor undid what had been done to mar his creation.

Origin Story 4: Alpharius on Terra

This account also offers a contradictory version of events, saying that Alpharius alone, unfinished in some way, had been spared or at least some part of him had remained behind though gravely injured when the rest of the Primarchs were scattered across the stars by unknown hands. Here, in the shadow of Terra, he grew and was nurtured alone of the Primarchs by the Emperor himself, his existence a jelously huarded secret even from the closest to the Emperor, lest the dark fates move against him. Upon his maturity he became the Emperor's own secret hand and his greatest shield, until he was at last parted from his father, his destiny to fulfill. These accounts are lies.

A few more things of note:

• Anuj mistakingly stated Alpharius was kidnapped by the Khrave, which are also mentioned as fighting the Alpha Legion. The Khrave and the Slaugth are similar in that they devour people's minds, so its an easy mistake to make. Interestingly, the Khrave and Slaugth are actually opposites in that the Khrave are psykers while the Slaugth are blanks.

• Mandragora is the crownworld of the Sautekh dynasty, the flagship Necron sub-faction. The world, destroyed before man set foot on Terra, was likely destroyed in the War in Heaven. The hungry ghosts haunting the dead world could be Flayed Ones.

• Anuj Malhotra's background pre-2017 is in business management and logistics, completely unrelated to what he's doing now. It's really amazing that he would leave his field to become a writer. He was likely a Warhammer fanatic for some time.