Roboute Guilliman
Roboute Guilliman (A.K.A.: Rowboat Girlyman, Rawbutt Girlyman, Robot Gulliver, Robot Gorillaman) is the Primarch of the Ultrasmurfs. He crash landed on Macragge as an infant, and as a result of the head trauma suffered massive brain damage and severely inflated his ego which only Commander Dante could rival. It is said, of the Primarchs, only Guilliman was retarded. He did, however, have a very large ego, and demanded that everyone who talked to him call him their spiritual liege. That being the only entry requirement to join the Ultramarines legion at the time, many thought it a fair trade for power armor. During the Horus Heresy, he was tricked by Horus with the promise of a shiny penny into deploying his legion into the middle of nowhere, and came back to find everybody else on Terra was dead, where his only comment upon arriving was "oops".
The few scattered space marine legions that were left, were in no condition to protect the Imperium as their ranks were either dead or defected to Chaos, so the Ultramarines was virtually the only chapter left to supplement the other chapters. After a hard day's thinking, Guilliman realized that all existence rested on his shoulders....we don't know exactly why but that's retardation for you, which explains today's Grimdarkiness. He quickly grew confused by this effort and sat down and made a coloring book, now known as the Codex Astartes. Its brilliance as a book only came about because Creed went back in time to ghost write it for Roboute, adding the now-familiar organizational scheme, which divided the Space Marine Legions into Chapters of more manageable size, and tactical doctrines for every situation, like the formidable Steel Rain.
One of his exploits was killing Alpharius (Or Omegon.... Or a standard Alpha Legion Space Marine.... We really don't know), the Primarch of the Alpha Legion, after taking the time to break-off from his stringent rulebook and think tactically for once. Alpharius wasn't a particularly hard fight since the Alpha Legion didn't embrace Chaos and so didn't have his dick pumped up with the ruinous powers, so he was still only as powerful as a normal Primarch, unlike Angron and Fulgrim who were mad powerful already with their Chaos pacts. However, he didn't count on the Alpha Legion to still keep fighting, even after the death of their Primarch, and so the Ultramarines had their asses handed back to them.
Much later, his throat was sliced by Fulgrim with a poisoned sword which should have killed him, or at least, should have been killed, but Guilliman has yet to realize that poison kills you, and so he spends his days frozen in place in a stasis tube, trying to remember which ninja turtle is which.
Also, since you are left fully conscious within a stasis tube, experiencing the last thing you felt before you went under... Yeah, daaaaaaaang.
Matt Ward has a hard-on for Guilliman due to daddy issues so he went all historical revision on his ass, and made him into the genius we think we know today as written in the 5th Space Marine codex.......that's just for canon terms anyway, the denizens of /tg/ still think of the Ultrasmurfs and anyone in it as they did in previous codex, which is to say like dicks.
The Codex, an Autobiography of Sorts
After the death of Horus and the near-death of the Emperor, Guilliman assumed the throne and became the Lord Commander of the Imperium, which granted him the same authority as the Emperor. While the other primarchs looked outward, intent on destroying the traitor legions and finding new recruits to rebuild their armies, Guilliman cast his furious gaze inward, towards the loyalist Space Marines themselves.
Guilliman was in a position of immense power at the time, possessing the strongest Space Marine legion, the most political sway, and more than enough resources to make any calls needed to repair the Imperium. What the fractured and devastated people needed most was a strong leader willing to take action and to resolve the problems the galaxy now faced. However, the primarch of the Ultramarines doubted his brother primarchs and their ability to stay pure for the unforeseeable future.
Hence, while he occupied the throne, he began work on the Codex Astartes: a work of pure insecurity and paranoia that would soon tear the Space Marines apart and make them more difficult to manage and rebuild than ever. Assuming the worst of his bretheren, and perhaps even his own men, Guilliman decreed that all Space Marine legions must be broken into chapters of no greater than one thousand, forcing them to act as more individualistic groups lacking in cohesive leadership.
Imperial historians hum, quietly, that there may have been alternatives at the time. The people were shocked at the force the traitor legions had brought to Terra, but many were certainly more interested in being protected from the ravages of the splintered traitors than they were in seeing the Imperium's best armed forces made disorganized. One possibility may have been consolidating all Marines into one force, organizing them like a real army with checks and balances, but Guilliman would have none of it.
Instead, he demanded the fragmentation of the Imperium's finest, which was frankly outrageous to the other primarchs. Rogal Dorn even sought to topple the decree, risking a civil war for the sake of keeping the Space Marines as functional groups that could fight and act as a whole. In the end, however, Dorn was too preoccupied with self-doubt, blaming himself for the death of the Emperor, and he eventually succumbed to Guilliman's plans.
What ensued afterward was what many acolytes now refer to as “a flipping paperwork nightmare”. Roughly one thousand documented chapters are known to exist, each which their own idiosyncrasies and movement patterns. They fly around the galaxy, attacking and defending whatever their chapter masters think is most important at the time, but they lack a unifying look at larger pictures without direct intervention from inquisitorial staff. As an elite military force, it is absolutely the worst possible way for them to exist in this time of strife.
Meanwhile, the individual chapters are known to infrequently go rogue or turn to Chaos, simply because they are so autonomous. They report to themselves alone, and often seize control of planetary governments. Rarely does the Imperium know what each chapter is trying to accomplish, and at times the Marines can go without supplies or support for years, which only increases the distance between the soldiers and the ideals they were meant to uphold.
Further outlining Guilliman's insecurities, the codex explains in great detail exactly how each chapter is meant to behave and approach every combat situation. The doctrine is unyielding, and some Marine chapters are known to severely punish officers that fail to uphold the codex. This micromanagement, too, was also widely reviled by the other primarchs. Corax was reported to have hissed at the document, insisting, “Theory cannot equip the mind with formulas for solving problems!” before spitting on the tome and hurling it at Guilliman's feet, an act which was not taken lightly between the two men. The Space Wolves still use the codex as toilet paper to this day.
Those bold enough to question wonder exactly what Guilliman's aim truly was. His codex weakened the other legions to considerable lengths. The white scars, which were known for their swift attacks, became encumbered by the increased organizational demands from the Codex, as one example. However, if Guilliman desired power over his fellow Marines, then why did he abdicate from power in such a short time after the Heresy?
Thanks to his fatal wound at the hands of Fulgrim, the Imperium may never know Guilliman's exact plans, and it is possible that such is for the best. If the past were any indication, what Guilliman had in store was more heavy-handed moderation, the likes of which may have crippled the Imperium further. After all, it is said that a weak and insecure leader will have weak and insecure armies, and weakness is what Guilliman brought to the Space Marines. Perhaps the codex speaks more about the man than he truly intended.