Inside Perturabo's private office on the bridge of the Iron Blood.
As the Iron Tsar leafed through the mountain of records concerning Roboute Guilliman and his Thirteenth Legion, the image of the brother Horus so despised—the one he labeled "ambitious"—began to take a clear shape in Perturabo's mind.
These public documents, detailing Guilliman's early history, allowed Perturabo Rurik Kislevsky to glimpse the true face of the master of Macragge.
The following is a summary reconstructed by Perturabo, based on these archives, regarding the first half of his "ambitious" brother's life.
Roboute Guilliman, the Thirteenth Primarch, had been swept away by a Warp storm while still an infant, just like Perturabo, Horus, and the others, scattered to the far reaches of the galaxy.
Fortunately, Guilliman landed on Macragge—a civilized world that had maintained its greatness and prosperity throughout the disasters of the Old Night. The infant Primarch was adopted by Konor Guilliman, one of the world's reigning Consuls, becoming the son the childless statesman never had.
To Perturabo's surprise, the records explicitly noted that, unlike other Primarchs, Roboute Guilliman had a "complete set of parents"—both an adoptive father and an adoptive mother.
His father was Consul Konor, and his mother was Tarasha Euten, a noblewoman who served as the chamberlain of the Guilliman household. She had overseen Guilliman's upbringing and education since his childhood. After Guilliman reunited with the Emperor and took command of his Legion, Lady Euten became the August Master of the Household on Macragge, managing all affairs of the Consul's residence.
According to the accounts, Guilliman displayed the singular talents of a Primarch from an early age. He graduated from Macragge's military academy at just ten years old—an age when his peers were barely halfway through their education—and immediately began his political career.
Upon graduation, Guilliman naturally became the youngest member of the Macragge Senate. Soon after, his father dispatched him to pacify the Illyrian tribes, barbarians who had long been at odds with the city-states of Macragge.
Instead of following the traditional route of an exhausting war of attrition, the young Guilliman chose a direct strike against the enemy's sacred sites. This forced the barbarians, who usually relied on guerrilla tactics, to engage his army in a decisive pitched battle.
In that final confrontation, Guilliman defeated the barbarian leader in single combat. However, he did not kill his opponent. Instead, he returned the sacred relics that ancient Macragge armies had looted from the tribes, seeking to forge a lasting peace.
Guilliman's magnanimity deeply moved the Illyrian tribes. They signed a peace treaty, vowing never to raise arms again. Thus, the young Roboute Guilliman pacified a conflict that had lasted nearly a thousand years through the most peaceful means possible.
Yet, when Guilliman returned in triumph, he found Macragge in chaos. Konor's enemies, fearing his reforms, had launched a coup while his powerful son was away at war. They murdered the Consul and attempted to overthrow the government.
After witnessing his beloved father's final moments, Guilliman led his army to suppress the coup. He suppressed his own desire for raw vengeance, instead organizing formal trials for the conspirators and executing them according to the law.
Subsequently, Guilliman became the youngest Consul in the history of Macragge. Under his wisdom, the world flourished. It was during this period of prosperity that the Master of Mankind arrived.
Upon reuniting with his gene-father, Roboute Guilliman took command of the Thirteenth Legion. Simultaneously, he established an independent realm with Macragge as its core—the "Five Hundred Worlds."
Having finished the records, a playful expression flickered on Perturabo's face. If he had previously constructed a mental image of an "ambitious" man based solely on Horus's brief remarks, he now had a much more intuitive impression of his brother.
"If Master Mikhail were assassinated by some nameless scum, I would personally execute the killers without a moment's hesitation. Whether they pulled the trigger or planned it from the shadows, I would never grant them a so-called 'trial.'"
"Yet Guilliman... this brother of mine managed to restrain his fury to give the murderers of his father a fair trial. That is truly astonishing."
"Perhaps this brother is more rational than anyone else."
Perturabo narrowed his eyes, muttering to himself. The fact that Guilliman chose a public trial over direct vengeance suggested a level of self-control that the Iron Tsar found remarkable.
"At the same time... let me see... he might also be an irredeemable idealist. A man who truly believes in law and justice. Hah, that Consul father of his must have been a genius to raise him with such idealism in a field as treacherous as politics."
"Or perhaps Konor Guilliman was the original idealist, wishing for his people to live in a comfortable world, and he passed that spirit onto his son."
Perturabo pondered further. Though the files did not explicitly state Guilliman's personality, the Iron Tsar—expert as he was in the intricacies of the human heart—could guess much from these early deeds.
"If that is the case, perhaps Guilliman simply wishes to build a peaceful world for his people. His 'Five Hundred Worlds' were born from that desire. He may not have any ambition for power for its own sake; or rather, he has already achieved his ambitions."
Perturabo squinted, beginning to form a definitive judgment on his brother.
"But this is only my guess. Perhaps when we meet, I will be surprised... or disappointed. Humans are complex, after all."
The Iron Tsar murmured to himself.
"My Lord, we have just received a distress signal from a Primarch!"
At that moment, Forrix entered the room in a hurry, dropping to one knee to report.
"Interesting! Which brother is calling for aid this time?" Perturabo asked, his interest piqued.
"It is—"
"It is the Primarch of the Seventh Legion, Lord Rogal Dorn. He is currently bogged down in an assault on a human world and requires the assistance of the nearest Imperial forces!"