'The Great Triumph,' nodded Ferrus sadly. 'I was on campaign in the Kaelor Nebula and too far distant to attend personally. It is the one regret I have, not being able to say my farewells to our father.'

'I was there,' said Fulgrim, his voice choked with emotion. 'I stood on the dais next to Horus and Dorn when the Emperor told us he was leaving, and it was the second most heartbreaking moment of my life. We begged him to stay, to see out what he had begun, but he turned his back on us. He would not even say what this great work was, only that were he not to return to Terra then all that we had won would crumble and fall into ruins.'

Ferrus Manus looked up at him, his eyes narrowed. 'You talk as if he abandoned us.'

'That was how it felt,' said Fulgrim, his tone bitter. 'How it still feels.'

'You said yourself that our father was returning to Terra to preserve all that we have fought and bled for. Do you really think he would not have wanted to see the final victory of the Crusade?'

'I don't know,' said Fulgrim angrily. 'He could have stayed, what difference would a few years make? What could be so important that he had to leave us there and then?'

Ferrus took a step towards him, and Fulgrim saw the reflection of his hurt anger in the mirrored eyes of his brother, the betrayal of everything he and the Emperor's Children had fought for over the last two hundred years.

'I do not understand what you imply Fulgrim,' said Ferrus, his words trailing off as the import of Fulgrim's earlier words came to him. 'What did you mean when you said it was the second most heartbreaking moment of your life? What could be greater than that?'

Fulgrim took a deep breath, knowing that he would have to come flat out and say what he had come to say.

'What could be greater than that? When Horus told me the truth of how the Emperor had betrayed us and planned to cast us aside in his quest for godhood,' said Fulgrim, relishing the horrified expression of surprise and fury on his brother's face.

'Fulgrim!' shouted Ferrus. 'What in Terra is wrong with you? Betrayed us? Godhood? What are you talking about?'

Fulgrim took quick steps to stand before Ferrus Manus, his voice passionate now that he had taken the final step and confessed his true reasons for coming here. 'Horus has seen the truth of things, my brother. The Emperor has already abandoned us and even now plots his apotheosis. He lied to us all, Ferrus. We were nothing more than tools to win back the galaxy in preparation for his ascension! The perfect being he pretended to be was a filthy lie!'

Ferrus pushed him off and backed away, his ruddy, craggy features pale and horrified. Knowing he had to press on, Fulgrim said, 'Others have already seen this truth and are moving to join Horus. We will strike before the Emperor is even aware that his designs have been unmasked. Horus will reclaim the galaxy in the name of those whose blood was spent to conquer it!'

Fulgrim wanted to laugh as the words spilled from him, the thrill of finally unburdening himself almost too great to stand. The breath heaved in his lungs, and he could not tell whether the thundering he could hear was the blood surging in his skull or the hammers of far away forges.

Ferrus Manus shook his head, and Fulgrim despaired as he saw his brother's horror turning to fury. 'This is the new direction of the Crusade you spoke of?'

'Yes!' cried Fulgrim. 'It will be a glorious age of perfection, my brother. What we have won is already being given away to imperfect mortals who will waste the glories we won for them. What we have earned in blood and tears will be ours again, can't you see that?'

'All I see is betrayal, Fulgrim!' roared Ferrus Manus. 'You are not talking about claiming back what we have won: you are talking about betraying everything we stand for!'

'My brother,' implored Fulgrim, 'please! You must listen to me. The Mechanicum has already pledged its support to the Warmaster, as have many of our brothers! War is coming, war that will engulf this galaxy in flames. When it is over, there will be no mercy for those on the wrong side.'

He saw the colour flood back into his brother's face, a raw and bellicose red that he knew all too well. 'Terms, I beg you for the sake of our brotherhood to join us!'

'Brotherhood?' bellowed Ferrus. 'Our brotherhood died when you decided to turn traitor!'

Fulgrim backed away from his brother as he saw the murderous intent in his blazing silver eyes. 'Lorgar and Angron are ready to strike, and Mortarion will soon be with us. You must join me or you will be destroyed!'

'No,' snarled Ferrus Manus, hefting Forgebreaker to his shoulder. 'It is you who will be destroyed.'

'Ferrus, no!' pleaded Fulgrim. 'Think about this. Would I come to you like this if I did not believe that it was the right thing to do?'

'I don't know what's happened to you, Fulgrim, but this is treachery and there is only one fate for traitors.'

'So… you are going to kill me?'

Ferrus hesitated, and Fulgrim saw his shoulders sag in despair.

'I am your sworn honour brother and I swear to you that I do not lie,' pressed Fulgrim, hoping that there was still a chance to convince his brother not to act in haste.

'I know you're not lying, Fulgrim,' said Ferrus sadly, 'and that's why you have to die.'

Fulgrim brought his sword up as Ferrus Manus swung his hammer for his head with blinding speed. The two weapons rang with a clash of steel that Fulgrim felt echo in the very depths of his soul. Flames blazed from his blade and lightning crackled from the head of Ferrus's hammer. The two primarchs stood locked together, Fulgrim pressing his fiery blade towards Ferrus, and the commander of the Iron I lands holding him at bay with the haft of his hammer.

Burning light and sound filled the Iron Forge, the weapons roaring as the unimaginable forces harnessed in their creation were unleashed. Ferrus dropped his guard and hammered his fist into Fulgrim's face, the force of the blow enough to crush the helmet of Tactical Dreadnought armour, but barely enough to bruise the flesh of a primarch. Fulgrim rode the blow and smashed his forehead into his brother's face, spinning on his heel and slashing his red hot blade towards Ferrus's throat.

The blade clanged on Ferrus's gorget, sliding clear without so much as scratching the black plate. Ferrus spun away from a return strike and swung his hammer one handed as he bought some space with his wide swings. The two warriors circled one another warily, both aware of how deadly the other could be, having fought side by side in decades of war. Fulgrim saw tears in his brother's eyes, and the mixture of sorrow and pleasure he took from the sight made him want to throw down his weapon and clasp his brother to his breast, that he might share such a stupendous experience.

'This is pointless, Ferrus,' said Fulgrim. 'Even now the Warmaster is preparing to expunge the weak from his forces at Isstvan III.'

'What are you talking about, traitor?' demanded Ferrus.

Fulgrim laughed. 'The power of four Legions will be unleashed against Isstvan III, but only those portions that are not loyal to the Warmaster and his grand designs for the future of the galaxy. Soon, perhaps even already, those weak elements will be dead, cleansed in the fire of a viral bombardment.'

'The Life Eater?' whispered Ferrus, and Fulgrim relished the horror he saw in his brother's eyes. 'Throne alive, Fulgrim, how could you be party to such murder?'

Wild laughter bubbled up inside Fulgrim, and he leapt to the attack, his blazing sword cleaving the air in a fiery arc. Once more, Ferrus's hammer came up to block the blow, but it was not a weapon designed for long duels, and Fulgrim rolled the blade over the haft and stabbed for his brother's face.

The burning blade scored along Ferrus's cheek, the skin blackening to match his armour, and his brother cried out as the sword he had forged dealt him a grievous wound. Blinded for the briefest second, he staggered away from Fulgrim.