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Warhammer 40K: Ultramar – Five Hundred Worlds, Under Guilliman

8 Minute Read
Aug 24 2022

The Realm of Ultramar has 500 Worlds and is considered a shining jewel of the Ultima Segmentum, ruled over by the Avenging Son and his Ultramarines.

Ultramar is the realm of the Ultramarines, and part of the greater Imperium. Unlike most Space Marine Chapters, the Ultramarines do not rule over a single world or fortress-monastery, but an entire sub-sector consisting of approximately five hundred habitable planets.


Ultramar, known as the Five Hundred Worlds, is a sub-empire within the Imperium of Man located in the southern reaches of the Eastern Fringe within the Ultima Sector of Ultima Segmentum. One of the furthest realms from the light of the Astronomican, Ultramar lies south of the Tau Empire and Ichar IV.

The Stellar Realm is divided into five sectors (North, South, East, West, and Center). Four of these sectors are ruled by a Tetrarch appointed by Guilliman himself. Every sector has a capital world where the Tetrarch oversees his section of Ultramar.

  • The Northern Sector is based around the Forge World of Konor. Its Tetrarch is Severus Agemman, First Captain of the Ultramarines.
  • The Southern Sector is based around the world of Andermung. Its Tetrarch is Second Captain Portan of the Genesis Chapter.
  • The Western Sector is based around the world of Protos. Its Tetrarch is Captain Balthus of the Doom Eagles.
  • The Eastern Sector is based around the world of Vespator. It had been previously ruled by a political entity known as the Sotharan league, but since Sotha was destroyed by Hive Fleet Kraken, Guilliman re-constituted what was left of the league around Vespator. It includes approximately 86 planets and Its Tetrarch is Decimus Felix, a Primaris Ultramarine recently promoted to Eleventh Captain of the Ultramarines and Equerry to Roboute Guilliman.
  • The Central Sector falls under the direct rule of Macragge and its regent, Marneus Calgar. It encompasses all systems in the heart of Ultramar with the exception of Konor, Veridia and Espandor, which fall under the remit of the Northern Tetrarch.

Ultramar History

Prior to the formation of Ultramar, the world of Macragge had maintained contact with its neighboring systems, its industries and peoples having largely survived the chaos of the Age of Strife. The world would be transformed however by Roboute Guilliman, becoming a prosperous and well-governed planet with trade routes that brought in raw materials and immigrants on a regular basis. It was during this time that Guilliman was rediscovered by the Emperor, who named him Primarch of the Ultramarines Legion and moved their forward base to Macragge. Within a year a new training base was operational and began taking recruits not only from Macragge, but from the surrounding systems as well. This close relationship with the other worlds would form the basis of what would become the Ultramarines’ stellar empire.

Great Crusade

During the Great Crusade, Ultramar maintained a steady supply of new recruits for the Legion, such that the Ultramarines became one of the largest Legions ever. It, along with the Ultramarines themselves, was left largely unscathed by the Horus Heresy, though it was invaded by the Word Bearers resulting in the Battle of Calth.In addition to that, about one-fifth of the Five Hundred Worlds was destroyed by the Word Bearers and World Eaters during the Shadow Crusade.In the aftermath of their campaign, the Word Bearers were able to erect the Ruinstorm, severing Ultramar from the rest of the Imperium. Guilliman became worried that the Imperium itself was lost and sought to have Ultramar become the heart of a new contingency empire: Imperium Secundus.


Post Heresy

With the end of the Heresy, Guilliman felt that Space Marines should no longer directly rule over Humanity and as a result removed most of the surviving worlds of Ultramar from Ultramarine control. Ultramar was reduced to a fraction of its former size. Ultramar was reduced to:

Ultramar was not attacked again until the War of the Beast when Ork forces landed on Quintarn and Prandium.Ultramar next came under attack in the First Tyrannic War with the invasion of Hive Fleet Behemoth. Though ultimately defeated, Behemoth would leave its mark, especially with the complete destruction of Prandium.

40th Millenium

Ultramar would be threatened a third time when the Iron Warriors Warsmith Honsou assembled an enormous warband to invade Ultramar and seek revenge against Captain Uriel Ventris. While the Chaos forces would be beaten back, the War for Ultramar would see the greatest loss of life since the Tyranid invasion of Hive Fleet Behemoth.


Later, after the Thirteenth Black Crusade Ultramar suffered yet another Chaos invasion, this time by the Black Legion. During the fighting, Roboute Guilliman was reborn and drove the invaders from Macragge, but left for Terra on the Terran Crusade. In his absence, Marneus Calgar and Tigurius were left to deal with the remaining Chaos forces.Guilliman declared that Ultramar’s original borders of the 500 Worlds was to be restored, and many of these resistant planets had to be forcibly reconquered. Shortly thereafter Gulliman re-instituted the Tetrarch system.

Shortly thereafter, the forces of Nurgle began to overwhelm Ultramar in a series of plagues and invasions known as the Plague Wars and Invasion of Konor. The traitor forces, led by Mortarion would initially make headway despite determined resistance by the Ultramarines and their allies. However, with the return of Guilliman and his Primaris reinforcements, the Nurglite invasion would be fought to a standstill. Their supply lines cut, their initiative lost and the Scourge Stars in peril due to the War in the Rift, the Nurglites chose to retreat from Ultramar.

There would then be a period of rebuilding, decontamination and fortification across the recently reformed 500 Worlds. Guilliman not only oversaw the reconstruction of Ultramar but also greatly increased its military strength to ward off future invasions.


Upon its assimilation into the greater Imperium during the Great Crusade, Ultramar became a state within a state, enjoying a large degree of autonomy that continues to this day. While all within Ultramar are subjects of the Emperor, the Supreme Leader of Ultramar was always Roboute Guilliman. After his wounding by Fulgrim, the leadership of Ultramar fell to the Lord Macragge with the Regent of Ultramar as his deputy. When Ultramar was a large realm of 500 worlds, there were Tetrarchs that operated below Roboute Guilliman from four key worlds. After the Heresy and the vast decrease of Ultramar in size, the post of Tetrarch was abolished but recently has been reinstated by the reborn Roboute Guilliman.

Below Tetrarchs were Imperial Commanders with connections to the Ultramarines. Each world of Ultramar is ruled by feudal lords loyal to the Chapter Master of the Ultramarines, which is why he is also known as Lord Macragge with all the rights and responsibilities the title entails. The government of each world, besides supplying the Ultramarines with men and material, is directed towards the prosperity of their populace.

Military Capabilities

Following the conclusion of the Plague Wars, Chapters besides the Ultramarines began to guard regions of Ultramar as well. Guilliman ordered that ten Chapters would be permanently stationed within Ultramar so the newly reformed 500 Worlds would be under the permanent protection of about 10,000 Astartes at all times. This included the Ultramarines and the Scythes of the Emperor who would receive extensive Primaris Space Marine reinforcements in order to replace their recent losses. The other eight were newly created Chapters from the Ultima Founding and consisted entirely of Primaris Space Marines. This increased military buildup was also so that future operations, such as the Vengeance Campaigns, could be conducted against the Scourge Stars and other regions around Ultramar that had been overrun by the enemies of the Imperium.


Defenders of Ultramar

The worlds of Ultramar do not pay the usual tithes, instead contributing directly to the upkeep of the Ultramarines Chapter. Though the need has diminished since the days of the Legion, each world still provides the Chapter with new recruits. It is a point of pride for a family to have provided a recruit, especially among the older aristocratic families, with many communities proudly displaying statues of the Ultramarines who were born there. For a family that has provided a renowned hero or even Chapter Master, the considerable fame and honor such a distinction provides can last generations.

Each world also maintains its own Planetary Defense Force, a well-disciplined and equipped force known as the Ultramar Auxilia. These forces are similarly exempt from the tithe system; however, the efficiency and prosperity of Ultramar is such that several hundred regiments are maintained to join the Imperial Guard when needed. As a result, the regiments of Ultramar have fought all over the galaxy, often in campaigns alongside the Ultramarines themselves.

Ultramar Auxilia soldier.

For space and orbital defenses, Ultramar can rely not only on the fleet of the Ultramarines but also the Ultramar Defense Fleet, the naval counterpart of the Ultramar Auxilia.Meanwhile no fewer than six massive star fortresses – with Galatan being the largest – stand sentinel over shipping lanes and critical strategic positions, each a formidable bastion protected by void shields and possessed of enough firepower to destroy a moon.

Learn More of the Worlds and Culture of Ultramar


~Aside from only Holy Terra, there may be no more advanced and prosperous portion of the Imperium. Make efforts to visit if you can Adepts!


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