The Dodekatheon, also known as the Brethren of Stone, was a warrior society of the Iron Warriors during the Great Crusade. The most influential of such societies, the Dodekatheon was an order of masons and strategies who origins pre-dated the Legion's connection to Olympia, instead originating from the Warcaste Metisraad culture of Terra. It focused on siege craft, strategy, and military fortifications. Upon reuniting with Perturabo, the Brethren were massively expanded. In theory the society was open to all Iron Warriors, but in practice it was only open to those who had proven themselves or attained Perturabo's favour.
Unlike warrior lodges in other Legions, there was nothing secret about the Dodekatheon. They typically met aboard the lead ship of present fleet elements, a meeting place for builders and warriors where new structural designs were unveiled, new theorems of war espoused, and battles both old and yet to come fought on simulator tables. All ranks were considered equal in the order, with the notable exception of the Honourable Soulaka. In spite of this nominal informality it was a vipers' nest of individuals vying for the favour of the primarch, with many alliances made and broken, and oaths sworn and forgotten, over the course of a meeting. First Captain Forrix found it particularly useful for assessing which warsmiths would work well together with the right level of rivalry.
After the outbreak of the Horus Heresy, a simulation table featuring the Imperial Palace became a permanent feature of the Dodekatheon aboard the Iron Blood. Warsmiths defended the palace using Imperial Fists doctrine in preparation for the Siege of Terra and, on one occasion, Perturabo himself was challenged by Kroeger — defeating the warsmith from both sides of the battle.
- Soulaka — Honourable, Apothecary
- Perturabo — Primarch of the Iron Warriors
- Forrix — First Captain
- Kroeger — Warsmith of the 23rd Grand Battalion
- Harkor — equerry to Kroeger, former Warsmith of the 23rd Grand Battalion
- Soltarn Vull Bronn — the Stonewrought, Warsmith of the 45th Grand Battalion
- Barban Falk — Warsmith of the 126th Grand Battalion
- Toramino — Warsmith of the 235th Grand Battalion, Master of the Stor-Bezashk
- Lucius — Lord Commander of the Emperor's Children, guest on exchange from the Brotherhood of the Phoenix
- Victrus Krugeran — Siege Captain
- Arkasi Achorax — Techmarine, primary gunner of Eradicant
- Mordan Vhosk — Techmarine, primary gunner of Obliteratus
- 1: The Horus Heresy Book Three pgs. 108–109
- 2: Angel Exterminatus (Novel), Chapter Eleven
- 3: Ironfire (Short Story)