After a round of communication, the Cosmic Xuanwu was confirmed as Guilliman's Fusion Beast.
The Cosmic Xuanwu was a very high-level Beast—not able to fuse with ordinary life forms.
It needed to fuse with a super lifeform to unleash its full power, so it wasn't a waste for a Primarch.
"All done, Rhodes?" Guilliman asked, coming over.
"It's all set. I picked the best match for you—it'll give you a real sense of security.
Let's just say, after fusing, you won't have to worry about other fallen Primarchs messing with you," Rhodes said.
Guilliman nodded in satisfaction. "What's this Beast's name?"
"It's called the Cosmic Xuanwu," Rhodes answered.
"That's an ancient Terra language, right? I've heard of Xuanwu—it's one of the four great guardian beasts," Guilliman said.
As a Primarch trained by the Emperor, Guilliman was well-versed in all Terran history and languages.
"Right! Xuanwu is the guardian of the North," Rhodes nodded.
"Alright, so after fusing with the Xuanwu, roughly how strong will I become?" Guilliman asked.
Elena had once been an ordinary Hospitaller Sister, even with some enhancements, never as strong as a proto-Astartes. After fusing with a Beast, she became Primarch-level and kept growing stronger.
Guilliman eagerly awaited what his Beast would do for him.
"First, you'll get gigantification—the Beast will enlarge you to at least 50 meters tall.
As you and it synchronize further, and you train more, your strength will keep increasing," Rhodes explained.
A Beast could let an ordinary being soar to the top, but for a super lifeform or Primarch, the increase was uncertain.
"Got it. What do I do next?" Guilliman asked.
Horus already got giant powers—now it was finally his turn!
"Simple: put your hand on this giant book, and the Beast will possess you," Rhodes said.
Following instructions, Guilliman put his hand on the main martial arts tome and instantly felt a surge of power.
"Your soul is strong, but your body is a bit weaker—slightly less than a super lifeform. Strange, such a powerful soul, but it doesn't match your body," a deep male voice echoed in Guilliman's mind.
"Hello, Cosmic Xuanwu. I'm Roboute Guilliman, Lord of the Ultramar 500 Worlds, Primarch of the Emperor. Let's fight side by side from now on," Guilliman replied, realizing this was the Beast.
He knew his soul and body were mismatched—Primarch souls were far stronger than their bodies.
"Yes, I'm satisfied with you. You're a perfect match for us Phantom Beasts—your soul is already super lifeform level. Our martial arts can boost the body, but the soul takes time.
But with your strong soul, after fusion, I can easily raise your body's level. It's a win-win," the Xuanwu said.
Indeed, boosting the soul was hard, but the body could be easily upgraded—technology or monster abilities could do that.
But having a soul to match a super lifeform body was rare.
Rhodes didn't even have a fully super-level soul—nor did his partner, just a half-super-level soul.
Most cosmic monsters or aliens had bodies stronger than their souls.
The Xuanwu's soul was top-tier super-lifeform level. After fusion, both would grow.
The Xuanwu turned into a yellow light and entered Guilliman. He instantly felt warmth all over, a powerful consciousness entering his body.
"Don't resist, partner! I'm using my power to upgrade your body to a super-lifeform level," Xuanwu's voice echoed in his mind.
Guilliman emptied his mind and relaxed, feeling a strange energy flow through him, transforming his body.
Every cell, every organ, grew stronger—a strange energy was remaking him.
The sensation even made Guilliman moan in pleasure; his soul felt supremely comfortable.
It was like before, his soul had been a giant squeezed into a small container, wearing children's clothes—uncomfortable but bearable.
Now his body was finally a proper vessel; the clothes fit—a true adult's outfit, comfortable and appropriate.
No more crowding; his soul was freed, his body elevated.
The feeling was wonderful!
He felt truly himself at last—this was the body his soul deserved!
Outside, Guilliman's body glowed gold, Xuanwu's yellow energy turning golden.
A gigantic golden turtle phantom appeared above Macragge.
Guilliman's body swelled, soon reaching a towering 60 meters.
Xuanwu's power became a golden suit of powered armor, attaching to Guilliman. A golden shield appeared in one hand, a golden sword in the other.
The whole of Macragge was stunned by the sight of a 60-meter-tall Roboute Guilliman.
"By the Emperor! Are you showing divine power?"
"O great Primarch! Glory to Macragge!"
Countless citizens and nobles knelt, worshipping the Lord of Ultramar.
Within the Ultramarines Chapter, Chapter Master Calgar, Chief Librarian Tigurius, and many captains—even returning veterans—were stunned by the giant Guilliman.
Their gene-father had become a terrifying giant, and as his gene-sons, they felt a surge of joy, as if their gene-father had truly found himself!
The happiest were the newly enhanced veterans—if a Primarch could become a giant, then their transformation was no longer a shame, but a supreme honor!
"I feel my gene-seed trembling—do you feel it?" Tigurius asked.
Primarchs and their gene-sons had a special link—physical and spiritual.
For example, when a Primarch died, all their sons felt it; when a Primarch grew stronger, so did they.
"I feel it too. I don't know what's happened, but our gene-father become stronger!" Calgar said, clenching his fists.
Calgar was now a 3.2-meter-tall juggernaut, having received the Primaris upgrade.
After more than ten minutes, Guilliman completed the fusion, opening his eyes to see his giant form.
Feeling the endless power and spiritual might inside, he sighed in awe.
"So, this is my true strength! This is how my soul and body should be."
He inhaled deeply, feeling unprecedented freedom and joy.
His true identity was the soul fragment of a god formed after the death of humanity's ancestral deity.
He was the true guardian of humanity; all Primarchs were meant to be like this.
The Emperor hadn't given them matching bodies, but now he had one—a body worthy of a Primarch.