With Horus joining, the rest of the Primarchs attacked as well. The Emperor wanted to ensure the Void Dragon's destruction, assembling a formidable force.
Guilliman shone with ochre light, using his cosmic Black Tortoise power to shield all his brothers with powerful energy barriers—stronger than void or psychic shields.
Magnus and Elena, after transforming, stood at the edge, launching waves of freezing attacks to slow the Void Dragon. Both had the weakest bodies among Primarchs, so they stuck to ranged attacks. Magnus, besides ice, unleashed powerful psychic assaults—second only to the Emperor.
Ice and psychic blasts rained down on the Void Dragon. Psychic energy was the most effective.
Lion El'Jonson and Vulkan, transformed, charged in. After fusing with the fire beast Golza, Vulkan was 80 meters tall, his weapons wreathed in flame. He smashed his hammer into the Void Dragon's belly, making it howl across the cosmos.
Lion raised his Tiger Soul Blade, surrounded by blue-white lightning—White Tiger wasn't just lethal, but also electric. Lion was like a thunder god.
"Come on, Xenos! Face me, the Emperor's firstborn, the First Primarch!" Lion roared, slashing and tearing at the monster, electricity and cold slowing the C'tan fragment to a crawl. Every Primarch used psychic attacks—the Emperor taught that psychic power was the best weapon against the Void Dragon.
Rhodes teleported around, building up energy, sometimes striking with his Steel-Breaking Fist or Ultra Shockwave, both infused with the Emperor's golden psychic energy—devastating to the Void Dragon.
Horus watched for openings, firing golden beams that the Void Dragon desperately avoided—one hit would mean defeat.
But dodging Horus meant taking hits from everyone else. The team effort battered the Void Dragon, with Guilliman tanking, shielding everyone.
Vulkan, Sanguinius, Lion, and Rhodes handled melee, while Rhodes and Sanguinius also healed with Phoenix Fire.
Magnus, Elena, and Horus provided ranged fire.
The Emperor summoned two avatars to join the melee.
Tartarus opened a portal, summoning Huron from Rhodes' territory, plus Magnus's former gene-son Ahriman, and Yvraine.
Yvraine, whom the Primarchs had met before, leapt into the fray wielding twin swords.
The other two drew curiosity. Ahriman was well-known.
"Don't worry—they're my subordinates. Focus on the Void Dragon," Rhodes said.
The newcomers joined the fight. Ahriman, fused with a cosmic beast, was almost as powerful psychically as Magnus. Huron, after Rhodes's modifications, was also formidable.
With these reinforcements, victory was assured.
"Ahriman, is that you? You follow Rhodes now?" Magnus asked, looking at his once-proud gene-son, the Thousand Sons' greatest sorcerer.
"Just focus on the fight, Father. I no longer have a gene-seed. With the cosmic beast's power, I'm a super-being on the level of a Primarch," Ahriman replied, fighting beside Magnus.
How nostalgic—last time they fought together was ten thousand years ago.
"Returning to the Imperium under Rhodes was the right choice," Magnus nodded. He was glad his gene-son had come back, even if not to his side.
"I'll keep trying to save those brothers who can be saved," Ahriman said while casting spells, testing Magnus's attitude.
"If you need my help, just ask," Magnus replied, understanding Ahriman's intentions. Magnus's answer pleased Ahriman.
"The cosmic beast's power can purify Chaos. If you're willing to help, I'll call on you," Ahriman said.
"Understood. What's your current identity?"
"I no longer use my old name. Lord Rhodes calls me Arim, and I'm his legion's chief strategist," Arim replied.
With this farewell to his gene-father, the name Ahriman was now history—he would serve Rhodes under a new identity.
He would not form his own Astartes legion, nor would the Emperor or Imperium allow it.
Magnus nodded and focused his rage into even fiercer attacks on the Void Dragon.
Arim smiled, wielding his staff to support Magnus in the assault.
"I've invented new sorcerer powers—some can control Chaos daemons. I'll teach you later."
"Good," Arim nodded. The name Ahriman was truly in the past now. The father and son had said their last goodbye; now they were like strangers.
"Curse you mortals! How dare you harm a god!" the Void Dragon raged. The battle had turned against him. He tried to escape, but found space itself sealed by some powerful force, unable to use C'tan powers to leave.
Staying meant certain defeat.
"You can't escape, Xenos. From the moment you tried to corrupt humanity, your fate was sealed," Rhodes sneered, unleashing his Steel-Breaking Fist.
A giant golden bull crashed into the Void Dragon, and the moment it faltered, freezing power immobilized its legs. Psychic binds, a flaming greatsword, and a warhammer pinned its arms, while a massive blade stabbed its chest, electricity surging and paralyzing it.
"Now, Horus—finish it!" Rhodes shouted.
Horus nodded, crossing his hands and forming a circle midair, golden energy gathering in his arms, then unleashing a powerful L-shaped beam.
The golden beam struck the Void Dragon, and the other Primarchs withdrew. The Void Dragon's body collapsed, unable to maintain its condensed form, losing all ability to fight.
Horus's ultimate attack, even at full power, would be deadly to the real Void Dragon, let alone a fragment.
The once-mighty Void Dragon was finished.
"We've won this war!" Lion declared.
"Yes, now release your cosmic beasts to suppress his power," Rhodes said, summoning his high-level cosmic beasts, and the others did the same.
Beasts that had already absorbed some C'tan fragments took the lead in suppressing the Void Dragon, helping the others to absorb C'tan energy.