Alpharius, Betaos, Gammon

Previously

Through the Great Crusade, there were rumors that the Hydras had no primarch, or many primarchs, or a primarch indistinguishable from his marines. From the outbreak of the Heresy War, this became regarded as established fact. 'Alpharius' was seen leading forces on both sides of the Heresy, frequently simultaneously though never on the same battlefield. For this reason, despite documented loyal service from many companies, particularly during the Battle of Terra, all marines of the Hydra were split among other Shadow Brotherhood companies and prohibited from passing on geneseed.

The remainder of this record was compiled from sensitive documents and is correspondingly restricted INDEX PROHIBITORUM INQUISITI

In the wake of the Heresy War, no one was so problematic to the remaining administration as the Hydra. Many treasonous sons of Alpharius surrendered to the loyalists, a dubious distinction they share with no other legion. Even the elements which stayed loyal surrendered to their brother legions, acknowledging the fact that outsiders could not reliably distinguish the Hydras and so their loyalty was also suspect.

The forerunners of the modern Inquisition, namely the Centuria Magnifica, Sisters of Silence, and Officio Assassinorum, applied extreme methods to confirmed traitors to find the truth.

All the surrendered Hydras believed they were following their Primarch, and had been for the duration of the war. They realized their error on the fields of Terra Herself, upon seeing Alpharius duel the Bloody Russ. Not all had been following the same master; at least two false primarchs (which the investigators assigned the identifiers Betaos and Gammon) directed significant portions of the legion during the Heresy War. Larger portions were in retrospect unsure whether their actions were loyal; the cell structure of the legion meant that they could have objectives without a clear picture of who set them or what overarching goal they served. At least one occasion was identified where Betaos and Gammon were working at cross-purposes.

This has remained one of the most frustrating open questions in the Inquisition's history. The Hydras have complex recognition codes, none more sophisticated than those for the primarch, which are the keys to the kingdom. That two entities, distinct and not aligned with each other, were able to impersonate Alpharius and maintain the ruse for years, is inexplicable.

In the centuries since, entities have come to light who present potential identities of the phony primarchs. A daemon known as The Changeling, in the service of Tzeentch, has become infamous among the knowledgeable for its ability to impersonate anyone, not being caught for months or years, both in daemon realms of the warp and in the materium. While it cannot be proven, there is general agreement that Betaos was most likely the Changeling.

The identity of Gammon is less clear, because best analysis suggests that the unknown actor was not furthering the cause of Chaos or any of its factions. It seems to have aimed to weaken both humanity and daemonity. Among the possibilities, and their caveats:

• An Eldar, most likely from the faction known as "Harlequins", who are skilled actors and quite deadly. Means and motive are both somewhat suspect, since while their capabilities are impressive they seem unlikely to be sufficient to the task, and similarly while they could gain from weakening us and the Great Foe, this is not in line with their usual observed behavior.
• A second daemon, otherwise unknown. While it is possible that such a daemon could have remained in the Immaterium ever since or been killed shortly thereafter, this provokes understandable skepticism.
• A xeno of unknown species, destroyed in the Great Crusade or the reconquering after the Heresy War. Here the main obstacle is capability; if any xeno race displayed traits suggestive of this level of capability, it was never recorded
• The newest theory is based on records of history and mythology from the metallic xenos known as "Necrons", also mentioned in some Eldar sources. They speak of 'living stars' who were revered as physical gods, and list the four most powerful as The Nightbringer, The Void Dragon, The Outsider, and The Messenger. Crucially, Eldar sources name the messenger "The Deceiver", and among its attributes are shapeshifting. Very recent sources, alleged to be from the 'Necrontyr remnant' after most of their species was transformed to metal, also identify the being as The Deceiver, and say it tricked their species into losing their very minds, giving them immortality in metal bodies but making them wholly tools of the star gods. All sources agree that the star-gods were innately hostile to the Immaterium and waged a war of conquest against the Materium. This line of inquiry requires further data.

A further secret is that the Alpha Legion was not destroyed. In every company are specialists trained elsewhere; techmarines on Forge Worlds of the Mechanicum, librarians on the Astronomicarks of the Magnificat, Witchbreakers on Titan (or its secretive sister sites in other Segmenta). The marines who depart for this training are not always those who return. One or two marines per company (more in Orders under strong suspicion) are in fact Hydra impersonators, who carry out their normal duties but also covertly watch their brothers for corruption or treason.

Others may be held as a secret strike force, working in squads or platoons; while no record I saw mentions this, I would not expect to have access to it if they did, and have opted not to inquire. Certainly some group must exist to train the substitutes.