The Hexagrammaton, colloquially known as the "Six Wings", were specialised formations that existed outside the regular chain-of-command and organisation of the Dark Angels Legion during the Great Crusade and Horus Heresy eras during the late 30th and 31st Millennia. These formations owed their existence both to the old Space Marine Legion formations of Terra, the amalgamation of the Terran pre-Principia Belicosa approach, the organisation of the later proscribed formations of the early Legiones Astartes, and the "Brotherhoods" of The Order from lost Caliban's knightly orders.
- "There is a tide in the affairs of men, which taken at the flood, leads on to fortune. Omitted, all the voyage of their life is bound in shallows and in miseries. On such a full sea are we now afloat. And we must take the current when it serves, or lose our ventures."
Before the creation of the first Space Marine Legions, the Legiones Astartes were organised into a formation known as the "Six Hosts of the Angels of Death", with each of these Hosts having its own specialisation and purpose. During the Wars of Unification the Six Hosts had each been created by the Emperor for a specific task, or from a particular type of warrior. Their names, if they had any, were unknown by the second century of the Great Crusade. These Hosts did not fight alone, being too specialised for general warfare on Terra and during the initial stages of the Great Crusade. Instead, elements of each Host were combined into battle groups of different sizes and designations. As and when required, the Hosts provided their troops to these armies depending upon the military need.
The warriors of each Host could be called upon when a particular threat or situation presented itself. The leader of a Host, chosen by his sect-brothers rather than appointed by the Emperor in those times, would assume temporary command of a battle or campaign so that their expertise could be deployed fully. It is not fully understood what happened to the Hexagrammaton in the other Legions and why its structure persisted only within the I Legion. For reasons only He knows, the Emperor chose not to continue with the Six Hosts and instead created the Principia Belicosa to structure the Legiones Astartes. The old ties of the Brotherhoods continued in the I Legion, though, and so the Six Hosts persisted in name and function. Being created from scratch, the later Legions were never built upon this foundation.
Following I Legion's reunification with their Primarch Lion El'Jonson on Caliban, the Lion incorporated the traditions of the Six Hosts with those of The Order. Thus, the Six Wings were created. The "Wings" of the Dark Angels existed beneath the structure of the Principia Belicosa that shaped the other Legiones Astartes, a substrate of organisation and tradition that predated the adoption of the structure of The Order of Caliban and even the amalgamation of the Six Hosts of Angels -- the Hexagrammaton -- but was also a result of both.
The I Legion did follow the principles of the later Principia Bellicosa, organising their Legion's strength into Chapters, led by Masters and Orders, which in turn were led by Paladins. These formations were further broken down into Companies, led by Captains. Members of the Six Wings were distributed amongst squads and companies, where they acted as Captains, Sergeants, and line Legionaries, or in specialised formations when assembled on orders from their respective voted-Lieutenant of a Wing. These Lieutenants acted as both commander of their Wing and often served as counsel to their Primarch. Voted-Lieutenants were elected by their peers rather than being nominated by a superior. They would then have their nominated successor chosen to command the Wing in the event of their untimely death, so as not to interrupt the cohesiveness of a Wing's command. On the field of battle, a commander responsible for an area of operations or campaign had to request the intervention of one of the Six Wings. When such a request was made and eventually accepted, the members of the requested Wing were summoned from their regular duties, when possible, in order to assemble and conduct operations under the command of their voted-Lieutenant's orders.
The Hexagrammaton formations that existed within the Dark Angels Legion at the time of the Great Crusade and Horus Heresy included the following: