Editing MidHammer 40,000 (section)

===Guilliman===
Title: The King Of Macragge.

Guilliman and the Ultramarines have become the go-to force for minor insurrections and problems around the Imperium's eastern fringes. Due to their facilities and many recruiting worlds they are the largest of the Astartes forces, but due to Guilliman having to work through literal mountains of paperwork and council often with the Warmaster, the King Of Macragge had to write the Codex Ultra, a Chapter-specific guide to how the Ultramarines should be run whenever their Primarch was unavailable, although he has made several thousand addenda and changes to it since he first wrote it just a few centuries after the Lorgar Letdown.

More recently, the Primarch has been said to have stepped off the battlefield to review historical combat data with intent to revise the Codex Astartes to be more in-depth, more flexible and an improvement all across the board, after having witnessed a tragic and shameful Ultramarines defeat at the hands of Tau, of all things, having been outplayed at every turn in a brutal and wasteful sequence of losses resulting in a miserable retreat from multiple Imperial sectors to consolidate the Chapter's forces. This event is already being called The Humbling, though not to Roboute's face.

Alternately:  Guilliman brought overwhelming force against the T'au, which they barely countered with clever tactics and highly-advanced technology.  When he then brought the full weight of Ultramar against them, they realized that no tactics were clever enough and no technology advanced enough to allow them to stand against the Imperium indefinitely.  Thus, they became reluctant Imperial vassals.

Guilliman is revising the Codex Astartes to include insights gained from costly battlefield experience against the T'au.  He is also seeking ways to integrate T'au technology into the Imperium.  He knows that he must tread very carefully in this endeavor and does not expect it to achieve any significant success for centuries:  The Ethereals are resistant to accepting aliens as their superiors, and the Adeptus Mechanicus view non-human technology as blasphemous.