"I didn't raise the Legion solely to build an Imperium and fight a crusade. Crusades are finite. Wars end. I raised the Legion to have a successive function in peacetime too -- as leaders, as statesmen, as rulers of the Imperium once it was built."
The title of Tetrarch, also sometimes given as Lord Martial, was a military and political rank utilised exclusively by the Ultramarines Space Marine Legion during the Great Crusade and Horus Heresy eras in the late 30th and early 31st Millennia and reestablished in the early 42nd Millennium. The Tetrarchs, combined with the Ultramarines Primarch Roboute Guilliman, comprised a governing body for the Realm of Ultramar known as the "Tetrarch Council."
The Tetrarch Council was responsible for administering the many institutions of the Five Hundred Worlds of Ultramar and were entrusted with its defence. Each Tetrarch was a military dictator of one of the five "king worlds" of Ultramar, and ruled over a sub-sector of that realm. The Tetrarchs, who were made up of four highly distinguished Veterans of the Ultramarines Legion, were appointed by the Primarch, who was himself Lord of the capital world of Macragge and the core worlds of Ultramar. However, the Primarch's duties as the governor of these worlds often fell on his seneschal in practice, while he led the armies of his XIII Legion on the Great Crusade.
The Tetrarch Council was revived by Roboute Guilliman following the end of the Indomitus Crusade in the second century of the 42nd Millennium when he and his forces returned to Ultramar to aid its defence against the servants of Nurgle during the Plague Wars. Guilliamn tasked each member of the reborn Tetrarch Council with once more expanding the Realm of Ultramar to include all five hundred of its original worlds.
During the latter years of the Great Crusade, the Five Hundred Worlds, as Ultramar was called colloquially in that ancient era, was divided up into four major fiefdoms under the overall dominion of the capital world of Macragge. This was done by the direct decree of Primarch Roboute Guilliman, the Lord of Ultramar, to improve the governance of his pocket stellar empire. Each of these domains was ruled from a major world within the realm by one of these "Princes of Ultramar." Every Tetrarch served as a military governor and provided the XIII Legion with a Champion and an Honour Guard. As each Tetrarch answered only to Roboute Guilliman himself and controlled several worlds, the rank was considered above that of any Planetary Governors of the Imperium or Chapter Masters of the Legion. The position was similar to that in rank and precedence of a Sector Governor in the Imperium of the late 41st Millennium.
One of the Ultramarines' most potent elite sub-formations was the Suzerain Invictarus. These Astartes formed the retinues of the five Tetrarchs of Ultramar, and functioned as both a military force for the defence of that fiefdom, arbiters of law for the population and an honour guard for their commander in battle. The individual forces of these Suzerain Invictarus varied in size, with Tetrarch Amyntas maintaining a force of several thousand as feared peacekeepers in the troubled worlds around Iax, while Tetrarch Lamiad had but one hundred in his guard, partly in deference to the Mechanicum warriors who stood in Konor's defence and did not need aid in doing so.
Preceding the Calth Atrocity, it was rumoured that Calth and its surrounding space were intended by the Primarch to become a new Tetrarchy, because of that Civilised World's growing industry, orbital shipyards and economic importance to Ultramar. Chapter Master Aetheon of the 19th Chapter of the Ultramarines Legion was rumoured to be Guilliman's choice to take up the role of the newest Prince of Ultramar. The devastating betrayal of the Word Bearers Legion put an end to that noble dream -- and much else besides.
It is unknown if any form of this administrative structure survived into the late 41st Millennium. In the wake of the Horus Heresy and Guilliman's own grants of sovereignty, the Five Hundred Worlds of Ultramar slowly broke apart into various autonomous domains, ultimately leaving the Second Founding Ultramarines Chapter with control over only the rump of Ultramar centred on Macragge, a mere 11 worlds of the five hundred that Guilliman once ruled. With the resurrection of Roboute Guilliman during the Ultramar Campaign of 999.M41 and his declaration that all five hundred worlds of Ultramar were once more part of his dominion, the Tetrarch Council was restored by Guilliman in his capacity as the ruling Lord Commander of the Imperium following the end of the Indomitus Crusade. The Tetrarchs were ordered to oversee the expansion of Ultramar back to its pre-Heresy size of five hundred worlds in the wake of the assault by the Daemon Primarch Mortarion and the other servants of the Plague God Nurgle during the Plague Wars.
The Tetrarch Council
The Lords Martial of the Realm of Ultramar in 007.M31:
|Roboute Guilliman||Lord Macragge, Primarch of the XIII Legion and Lord of the Five Hundred Worlds|
|Eikos Lamiad||Tetrarch of Konor|
|Tauro Nicodemus||Tetrarch of Saramanth|
|Valentus Dolor||Tetrarch of Occluda|
|Stolos Amyntas||Tetrarch of Iax|
The known Lords Martial of the Realm of Ultramar in 111.M42 after the reestablishment of the Tetrarchy following the Plague Wars:
|Roboute Guilliman||Lord Commander of the Imperium and Lord of the Realm of Ultramar||Primarch of the Ultramarines Legion||Governor of the Realm of Ultramar|
|Severus Agemman||Tetrarch of Konor||First Captain of the Ultramarines Chapter||Expanding Ultramar's territories to the galactic north|
|Portan||Tetrarch of Andermung||Captain of the Genesis Chapter's 2nd Company||Expanding Ultramar's territories to the galactic south|
|Balthus||Tetrarch of Protos||Captain of the Doom Eagles Chapter||Expanding Ultramar's territories to the galactic west|
|Decimus Felix||Tetrarch of Vespastor||Eleventh Captain of the Ultramarines Chapter||Expanding Ultramar's territories to the galactic east|
- The Horus Heresy - Book Five: Tempest (Forge World Series) by Alan Bligh, pp. 38, 50, 68, 81-82, 133
- Know No Fear (Novel) by Dan Abnett
- The Unremembered Empire (Novel) by Dan Abnett
- A Deeper Darkness (Short Story) by Rob Sanders
- Gathering Storm - Part Three - Rise of the Primarch (7th Edition), pg. 44
- Dark Imperium (Novel) Guy Haley, Ch. 20 "The Council of Hera," pp. 240-243