"It would take a long time to relate the 7 years of war that I faced when my gene-sire betrayed his own Father, the Emperor of Mankind, so I shall give you a shortened version. I hope you forgive the telling, I am not a word smith or poet."

He takes a deep breath and begins, "I was part of the greatest undertaking mankind had ever known, the Great Crusade which brought the enlightenment of the Imperium of man out into the darkest reaches of the galaxy." He looks wistful, remembering that century of glory and hope.
"I rose to command, I suppose by my own merits. I was taken into the confidence of my gene-sire Horus Lupercal. Myself and 3 other battle brothers made up his mournival. We were his advisors and companions, and often acted to express opinions he could not, for reasons of politics." He smiles a little, remembering the brotherhood as it was, then continues. "But Horus betrayed the Emperor, and in doing so betrayed me as well, trying to engineer the death of his loyal sons in a massacre disguised as a compliance action on a rebellious planet. He had brought some of his brothers, the other Primarchs on as his allies, and they rampaged across the galaxy, tearing the Imperium apart. I fought against him, for he did not manage to have me slain, and confronted him again a few years later. He tried to recruit me to his side, and I denied him. The traitor forces have pushed us back to Terra, the very palace itself set high in the Himalasyan mountains and I fought two of my traitorous mournival brothers at the Saturnine gate. I slew them both. And then..."

He lowers his head. "I ended up here, my oath to fight to the death broken, or at least delayed."