The ending bit.
"The Chapel of the Dioskuri was silent. Polixis' head had been bowed as he related his confession, but he raised it now to meet the red visor lenses of Kastor's skull helm.
The Chaplain reached up and disengaged the sealant lock, removing the grim piece of armour and setting it on the altar with a thud. The face revealed was the same as Polixis' -- firmly set, dark-eyed, with hair the colour of a golden harvest. The similarities went beyond the changes wrought by a primarch's shared genetics.
'Do you remember when I saved the pup from the waters of the Icaldon?' the Chaplain asked. Polixis remained looking up at him, processing the question. The fact that Kastor had removed his helmet broke with the protocol of the confessional.
'I do not,' the Apothecary admitted eventually. 'You know my memories of those days are less complete than yours.'.
'Morik the agri-master's flock-hound had plunged into the river and its pup had followed,' Kastor said. 'Both were swept away. I pursued them, and you would have followed had father not dragged you back. I managed to reach the pup, but its mother was gone. I could not save them both.'.
'A pup is a different matter to a brother of the Fulminata--' Polixis began to say, but Kastor raised his hand for silence.
'I have only one question for you,' he said. 'Have you come here to confess your guilt to the Chaplain of the Fulminata, or have you come to confess it to your blood-brother?'.
Polixis said nothing.
'Your silence is an answer in and of itself,' Kastor said. 'You have committed no crime worthy of a confession. The tactical situation was clear and the Codex supports your actions. Tulio was lost, and the fact you recovered the daughter of the de la Sarios was an achievement that you should look back on with pride. With her gene-lock we were able to access the weapons vault and turn the orbital defences on the heretics. Had it been the other way around, the entire strike force would have been decimated, and the world of Atari lost.'.
'But could I not have recovered both her and Tulio?' Polixis said. 'The Imperium needs warriors, now more than ever. The loss of even a single battle-brother's legacy is a grievous failing. I alone am accountable for that.'.
'The Imperium needs humanity,' Kastor corrected. 'That is the very reason that we exist -- to preserve mankind and all of its great works. You are right to speak of legacy. You preserved a legacy when you saved that girl. She will never forget that her life was paid for by one of the Emperor's warrior. In righteous likelihood, she will grow up to be a firm and righteous leader, one ever-mindful of the dangers that threaten the Imperium and the warriors that stand ready should she have need.'.
Polixis sad nothing as he considered his brother's words. Kastor went on.
'You are right -- a pup cannot be compared to the memory of brother Tulio. But Agri-master Morik rejoiced when I emerged from the swell with the dog in my arms. He knew that the future of his flock was secure. And the Imperium's future will be secure too, so long as we make the sacrifices required for victory. Atari still stands because you completed the mission. If some of our number are lost -- even you or I -- in doing so, that is not something to mourn. It is both our duty and out privilege. You should not hold it against yourself either. That we must suffer on occasion is inevitable. We are warriors.'.
'It is a difficult lesson,' Polixis admitted. 'One that I fear I must relearn every time. It still hurts.'.
'And that is to your credit,' Kastor said, extending one gleaming, black-armoured hand. Polixis grasped it, the white gauntlet meeting the black, thumb-to-thumb, the brother's grip rather than the warrior's. He stood.
'We are a torch, set aside for mankind's darkest hour,' Kastor said. 'That hour is upon us now. May we burn brightly, you and I, and never waver. We owe that to Tulio's memory, and the future lives of those we save.'."