Writings
Several of the Primarchs had literary inclinations. Fulgrim was quite a talented poet, though he never really invested much in this skill, preferring to concentrate on perfecting his sculptures. Rogal Dorn had written two brutally honest reviews, which to this day serve as an example for many an Imperial critic. Vulkan's letters have avoided being published until the 36th millennium, but once made available to the Imperial scholars, have given them a new perspective on the Primarch.
Out of them all, Roboute Guilliman stands out as the one who has written most. Chief among his works is of course the Codex Astartes, but it is not the only one. Eschewing more frivolous pursuits, the Primarch of the Ultramarines concentrated instead on purely utilitarian literature. He had penned several manuals and guides, many of which are still used by various branches of the Imperial administration and military.
Notable amongst them is the Educatio Veneris per Stultum, not only because it retains its usefulness until today and is often used by Commissars of the Imperial Guard when they have to address the issue of safe sexual conduct, but also because it is the only writing of their Primarch that the Ultramarines refuse to talk about. A reason as to why has yet to be determined, although an anonymous Space Wolf had once commented that it's the only book that doesn't read like the writings of "a complete and utter stuck-up asshole." (1)
Another interesting position from Guilliman's list of writings, is the lesser known essay Sculptura de Macragge. It's one of his earliest pieces of writing, having been composed before he even became the Consul of Macragge. (...)
From Introduction to Imperial Literature
Roboute Guilliman was upset. It was not a usual state of mind for him. Generally, he remained content with his life, but not on that day.
It was all his father's fault. What gave him the idea that leaving his only son to take care of his young cousin was a good idea, Roboute would never guess. The girl was three. Well, Roboute was three too, but unlike the girl he could easily pass for an adult. Or maybe he was an adult?
The matter of his age and his maturity was a constant source of confusion for him. He simply had no idea how to think of himself and that just didn't sit well with him. Being around children only made the feeling more acute. Predictably, Roboute did not like children and tried to avoid them when possible.
He gave the little girl a wary look. She, in retaliation, stuck out her tongue.
"Nu-uh," she sing-sung. "You've gotta listen to me, 'cause I'm older."
He really hated doing this, but he was feeling existentially challenged and the girl's argument was so damn irrational; he just couldn't come up with a good retort.
"My birthday is actually the day father found me," he pointed out, trying to sound reasonable. "I'm probably older than you."
"No fair," the child grumbled, pouting and crossing her arms peevishly. "I'm gonna tell mommy you're mean."
He recognized the moment in the child-adult interaction as the one where he needed to resort to bribery to get some peace. Well, perhaps bribery was a harsh word.
"We're going for a walk," he said, picking the girl up.
"I wanna see the ponies," his cousin announced, grinning at him for some mysterious reason.
"You've seen them the last time," Roboute pointed out. On his list of utterly boring and useless things, ponies ranked pretty high. They were only good for children to ride on until they were big enough to ride a horse and riding a horse was damn useless, if you had a vehicle to use instead. "How about we go somewhere new?"
It was cheating a bit, he supposed, but then he wanted to go to the park: he was supposed to write about art for one of his tutors and there was a new sculpture there. But children liked parks, didn't they? So it should turn out alright.
(1) Interestingly enough, the latest editions have been supplemented with a chapter regarding the Genestealer threat written by Chaplain Ortan Cassius.
(2) Incidentally, most of Guilliman's writings about Macragge are works written for his tutors.
From Introduction to Imperial Literature
AN:
Roboute's cousin is another effect of "hm, but they must have had a life outside of being awesome warriors of awesomeness TM".
I'd also like to thank Pixo for beta-reading. :)