Tetrarch - History: 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 XIIIth Legion with a Champion and an honour guard drawn from the Legion's Invictarus Suzerain.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 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 Suzerains Invictarus varied in size, with Tetrarch Stolo Amyntas maintaining a force of several thousand as feared peacekeepers in the troubled worlds around Iax, while Tetrarch Eikos Lamiad had but one hundred in his honour guard, partly in deference to the Mechanicum warriors who stood in Konor's defence and did not need aid in doing so.Preceding the Battle of Calth, 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 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 and Imperial Regent following the conclusion of the first phase of the Indomitus Crusade with the stabilisation of the Imperium Sanctus in the wake of the Great Rift's birth.The restored 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.