"Roboute Guilliman? Which brother is this? And why do you say he is an ambitious man?"
Upon hearing Horus's dismissive attitude toward Guilliman, Perturabo Rurik Kislevsky asked with a hint of confusion. He hadn't expected Horus to hold such a low opinion of one of their own kin.
"Heheheh—"
"Perturabo, my brother, if building one's own little kingdom under the Emperor's very nose and carving out a realm to rule as a king isn't considered 'ambitious,' then I fear no one in this world earns that title."
Hearing Perturabo's puzzled inquiry, Horus let out a cold, faint laugh. The Lupercal held little affection for Roboute Guilliman, a Primarch who remained notably distant from his other brothers.
"Interesting. It sounds like this brother is someone worth knowing. Though, Horus, I won't simply take your word for it."
The Iron Tsar, who maintained a high level of wariness toward Horus due to the Lupercal's excessive influence over his own sons, responded firmly, indifferent to Horus's reaction.
"Haha, Perturabo, my brother, since that is your stance, I shall not bother listing Guilliman's ambitions any further. Just know that he is a brother with immense aspirations."
Seeing that Perturabo wasn't buying into his rhetoric, Horus grinned and answered slowly.
"Then, what do you plan to do with this former Ork world? Will you hand it over to those mortal bureaucrats of the Administratum, as you suggested?"
Instead of answering Horus directly, Perturabo glanced around his surroundings and asked.
"What else? Do you think I am the type to carve out a kingdom like Guilliman? Naturally, I will hand this place over to the mortals of the Administratum. Whatever happens here afterward is none of my concern."
Horus waved his hand impatiently at the question. It was clear the Sixteenth Primarch had little interest in the finer points of governance. To him, Perturabo's inquiry seemed somewhat nonsensical.
Hearing Horus's dismissive reply, Perturabo slightly raised an eyebrow, a plan forming in his mind.
"Lord Horus Lupercal, my elder brother, may I then take charge of this planet? I wish to incorporate this world into the political entity known as the 'Tsardom of Kislev,' belonging to my Fourth Legion."
"As a reward for leading the Fourth Legion to fight alongside you, the honor of conquering the Orks shall belong to you and the Sixteenth. However, the practical benefits of ruling this world shall go to me and my Fourth Legion."
After a brief moment of thought, Perturabo made his request, seeking his brother's opinion.
"You wish to include this in your domain, brother?"
"Well, you are a Primarch, Perturabo. It is your prerogative to choose where you rule directly. I imagine that if you personally declare this world your territory, those mortal bureaucrats won't be foolish enough to ask you to relinquish it."
Horus gave him a strange look, seemingly genuinely surprised by his brother's request.
"Then this world belongs to me. I will migrate countless Kislevite peasants here and transform this world, once despoiled by Orks, into yet another prosperous and wealthy human realm."
Perturabo nodded slightly, satisfied with the answer.
Aboard the Iron Blood, the Gloriana-class flagship of the Fourth Legion, Perturabo led his fleet back onto the path of the Great Crusade after parting ways with Horus.
Of course, before leaving world "33—89," Perturabo left behind a detachment of mortal soldiers and bureaucrats. Their job was to manage the handover with the incoming Imperial Administratum officials, making it clear that this newly conquered world now belonged to the Iron Tsar and his Tsardom of Kislev, and was no longer directly accountable to the Administratum on Terra.
Meanwhile, Horus led the Luna Wolves and the 63rd Expeditionary Fleet in the opposite direction to continue their exploration and conquest. Perhaps the Sixteenth and Fourth Legions would have countless opportunities to fight side-by-side in the future, but for now, this joint operation had ended. Led by their respective Primarchs, the two legions set off on diverging paths.
"Forrix, find me all available data on Roboute Guilliman, Primarch of the Thirteenth Legion. I find myself quite interested in this brother of mine. I want to understand him before I meet him in person."
Sitting upon his throne in contemplation, the Iron Tsar called for his subordinate. During their conversation, Horus had tried hard to paint a picture of Guilliman as a villain.
Yet, the more Horus sought to blacken Guilliman's name, the more curious Perturabo became. Horus's high level of influence over the legions had already made Perturabo instinctively repulsed by his words, driving him to investigate Guilliman's character for himself.
"As you command, my lord. I will bring you all the records concerning Lord Roboute Guilliman."
Forrix nodded and immediately ordered his mortal servants to begin gathering a series of files regarding Guilliman and the Thirteenth Legion.
Before long, Perturabo's desk was piled high with public records—from the founding of the Thirteenth Legion to the current establishment of the Five Hundred Worlds of Ultramar—for the Iron Tsar's personal review.
"Heh, Horus Lupercal... the more you try to smear our brother Guilliman, the more curious I get. You've truly achieved the opposite effect!"
Perturabo let out a cold laugh as he flipped through the documents.
"Roboute Guilliman, my brother... let me see exactly what you have done to make Horus so jealous, and so full of loathing for you."
"Perhaps when we finally meet, we might find ourselves to be the best of friends. Let me get to know you well, Roboute Guilliman."
Perturabo's expression turned playful as he muttered to himself.