An Ultramarine? Going rogue? Did someone turn him into a Soul Drinker or something?
In the wake of the calamity that was the Horus Heresy, the foundations of the Imperium of Man were laid down. The first High Lords of Terra established the structure by which the Adeptus Terra operated, and described the feudal responsibilities and duties of the planetary lords. One of the most important accomplishments was the reorganisation of the Imperium's fighting forces. This was undertaken almost single-handedly by the Primarch of the Ultramarines Legion, Roboute Guilliman, who with characteristic speed and efficiency codified the structure of the Imperial Guard, the Imperial Navy, and the Space Marines. Of all of his works, the most influential is the Codex Astartes, the great prescriptive tome that lays down the basic organisational and tactical rules for the Space Marine Chapters.
The Horus Heresy had revealed previously unknown genetic weakness in the gene-seed of the Primarchs and Space Marines among the original 20 First Founding Space Marine Legions, weaknesses that left the Legions in question greatly exposed to corruption by the Ruinous Powers of Chaos. This risk was exacerbated by the rapid nature of Space Marine recruitment during the centuries between the start of the Great Crusade in ca. 800.M30 and the outbreak of the Horus Heresy itself in the early 31st Millennium. With the Imperium of Man expanding so quickly across the galaxy during the Great Crusade, the need for fresh recruits in the Space Marine Legions was great. So much so that some Legions had not been as particular in their gene-seed screening practices and recruit selection processes as they should have been. The first objective of Roboute Guilliman in writing the Codex Astartes was to both recognise and purge these weaknesses.
Following the end of the Horus Heresy and the retreat of most of the Traitor Legions into the Eye of Terror, the Codex decreed that the nine remaining Loyalist Legions would be divided into 1,000-man Chapters, the Chapter Masters of which would be directly beholden to the Emperor Himself and no other, not even the Primarchs of their original founding Legions (save in the case of the single Chapter that would remain under each Primarch's control and retain its Legion's original name). No one man in the Imperium could ever again control the superhuman might of an entire Legion of 100,000 or more Space Marines.
The Codex outlined a new, more measured process for Space Marine selection and recruitment and insisted that each newly-created Successor Chapter would tithe 5% of its genetic material to the Adeptus Terra and the Adeptus Mechanicus for testing and monitoring. It also decreed that only the Emperor Himself, through the auspices of the High Lords of Terra, would ever again be able to order the creation of a new Space Marine Chapter. All gene-seed would be subjected to the greatest genetic scrutiny before being used in the creation of new Space Marine implants. To prevent cross-contamination, the Codex rebuked the practice of sharing gene-seed between different Chapters and, henceforth different Legions with their different genetic make-ups. From then on, each Chapter would have to rely solely on the gene-seed produced in the bodies of its own Space Marines.
On Terra, the Adeptus Terra created genetic repositories to produce and store Space Marine gene-seed. These banks were used to provide all new gene-seed for Space Marines and, to prevent cross-contamination, the genetic material of each of the old Legions was isolated. Henceforth, the new Space Marine Chapters would receive gene-seed only from their own genetic stock. The remaining gene-seed of the Traitor Legions was placed under a time-locked stasis seal, although at the time, many believed these dangerous stocks should be destroyed. By taking direct control of the genetic stocks, the Adepts of Terra could ultimately control the Space Marines. Now they alone had the power to destroy or create Space Marine Chapters at will.
The Codex also further defined the accepted tactical doctrine, Chapter organisation, order of battle, and recruitment practices for a Space Marine Chapter. It explained the different battlefield roles assigned to each squad of Space Marines in a Chapter, defining them as Tactical, Assault or Devastator Squads and assigning different equipment and purpose to each (see the excerpts below).
There were many other topics covered in the Codex and all of them displayed Guilliman's formidable intelligence and hard-won wisdom. The most controversial and yet most important of the topics and decrees made in the Codex Astartes was that the original twenty Space Marine Legions consisting of 10,000 to upwards of 200,000 Astartes or more, were divided into new Chapters, an existing organisational formation found in the old Legiones Astartes. One Chapter kept the name and colours of the original Legion, while the remaining Chapters took on new titles and colours. Most of the old Legions were divided into fewer than five Chapters, but the Ultramarines, being by far the largest of the Legions, were divided many times. The exact number of new Chapters created from the Ultramarines is uncertain: the number listed in the oldest known copy of the Codex Astartes (the so-called Apocrypha of Skaros) gives the total as 23, but does not name them. These Chapters would consist of ten companies of 100 Space Marines each. The breaking of the remaining nine Loyalist Legions into multiple Space Marine Chapters is known to Imperial historians as the Second Founding, which occurred in ca. 021.M31, seven standard years after the death of Horus.
Is this a new Horus Heresy thing? As far as I know, Guilliman wrote the codex.el_kabong said:
In the wake of the calamity that was the Horus Heresy, the foundations of the Imperium of Man were laid down. The first High Lords of Terra established the structure by which the Adeptus Terra operated, and described the feudal responsibilities and duties of the planetary lords. One of the most important accomplishments was the reorganisation of the Imperium's fighting forces. This was undertaken almost single-handedly by the Primarch of the Ultramarines Legion, Roboute Guilliman, who with characteristic speed and efficiency codified the structure of the Imperial Guard, the Imperial Navy, and the Space Marines. Of all of his works, the most influential is the Codex Astartes, the great prescriptive tome that lays down the basic organisational and tactical rules for the Space Marine Chapters.
The Horus Heresy had revealed previously unknown genetic weakness in the gene-seed of the Primarchs and Space Marines among the original 20 First Founding Space Marine Legions, weaknesses that left the Legions in question greatly exposed to corruption by the Ruinous Powers of Chaos. This risk was exacerbated by the rapid nature of Space Marine recruitment during the centuries between the start of the Great Crusade in ca. 800.M30 and the outbreak of the Horus Heresy itself in the early 31st Millennium. With the Imperium of Man expanding so quickly across the galaxy during the Great Crusade, the need for fresh recruits in the Space Marine Legions was great. So much so that some Legions had not been as particular in their gene-seed screening practices and recruit selection processes as they should have been. The first objective of Roboute Guilliman in writing the Codex Astartes was to both recognise and purge these weaknesses.
Following the end of the Horus Heresy and the retreat of most of the Traitor Legions into the Eye of Terror, the Codex decreed that the nine remaining Loyalist Legions would be divided into 1,000-man Chapters, the Chapter Masters of which would be directly beholden to the Emperor Himself and no other, not even the Primarchs of their original founding Legions (save in the case of the single Chapter that would remain under each Primarch's control and retain its Legion's original name). No one man in the Imperium could ever again control the superhuman might of an entire Legion of 100,000 or more Space Marines.
The Codex outlined a new, more measured process for Space Marine selection and recruitment and insisted that each newly-created Successor Chapter would tithe 5% of its genetic material to the Adeptus Terra and the Adeptus Mechanicus for testing and monitoring. It also decreed that only the Emperor Himself, through the auspices of the High Lords of Terra, would ever again be able to order the creation of a new Space Marine Chapter. All gene-seed would be subjected to the greatest genetic scrutiny before being used in the creation of new Space Marine implants. To prevent cross-contamination, the Codex rebuked the practice of sharing gene-seed between different Chapters and, henceforth different Legions with their different genetic make-ups. From then on, each Chapter would have to rely solely on the gene-seed produced in the bodies of its own Space Marines.
On Terra, the Adeptus Terra created genetic repositories to produce and store Space Marine gene-seed. These banks were used to provide all new gene-seed for Space Marines and, to prevent cross-contamination, the genetic material of each of the old Legions was isolated. Henceforth, the new Space Marine Chapters would receive gene-seed only from their own genetic stock. The remaining gene-seed of the Traitor Legions was placed under a time-locked stasis seal, although at the time, many believed these dangerous stocks should be destroyed. By taking direct control of the genetic stocks, the Adepts of Terra could ultimately control the Space Marines. Now they alone had the power to destroy or create Space Marine Chapters at will.
The Codex also further defined the accepted tactical doctrine, Chapter organisation, order of battle, and recruitment practices for a Space Marine Chapter. It explained the different battlefield roles assigned to each squad of Space Marines in a Chapter, defining them as Tactical, Assault or Devastator Squads and assigning different equipment and purpose to each (see the excerpts below).
There were many other topics covered in the Codex and all of them displayed Guilliman's formidable intelligence and hard-won wisdom. The most controversial and yet most important of the topics and decrees made in the Codex Astartes was that the original twenty Space Marine Legions consisting of 10,000 to upwards of 200,000 Astartes or more, were divided into new Chapters, an existing organisational formation found in the old Legiones Astartes. One Chapter kept the name and colours of the original Legion, while the remaining Chapters took on new titles and colours. Most of the old Legions were divided into fewer than five Chapters, but the Ultramarines, being by far the largest of the Legions, were divided many times. The exact number of new Chapters created from the Ultramarines is uncertain: the number listed in the oldest known copy of the Codex Astartes (the so-called Apocrypha of Skaros) gives the total as 23, but does not name them. These Chapters would consist of ten companies of 100 Space Marines each. The breaking of the remaining nine Loyalist Legions into multiple Space Marine Chapters is known to Imperial historians as the Second Founding, which occurred in ca. 021.M31, seven standard years after the death of Horus.
. 
