Roboute Guilliman is the Primarch and Founder of the Space Marines. Guilliman is the Primarch who single-handedly reshaped the Imperium of Man after the first Multiverse war, taking the lead role in reforming the administrative and military apparatus of the Imperium following the Imperium joining the Allies. Guilliman is perhaps best remembered for being the author of the Codex Astartes, a key volume that laid out the proper tactics and military organisation for the majority of Loyalist Space Marine Chapters now in existence. Roboute Guilliman is also one of the few Loyalist Primarchs still alive.