Diocletian Coros rose to the rank of Tribune in the years of the Heresy, one of the senior officers upon whom Valdor relied to translate the Emperor's will into deeds across a fracturing Imperium. He was a Custodian of cold clarity, given to seeing a campaign whole where others saw only the battle before them, and he bore the burden of decisions that spent golden lives for strategic ends. Where the Legio ventured beyond Terra during the war, it was often a Tribune such as Diocletian who commanded, carrying the Emperor's authority into warzones the primarchs could not reach.
He was not without doubt; the silences of the Master of Mankind troubled him as they troubled Valdor, and he came to understand how much of the war's true shape was hidden even from the Ten Thousand. Yet doubt never dulled his blade. Diocletian fought through the defence of Terra with the same unflinching resolve he brought to every duty, a warrior who had long since made peace with the certainty that his kind existed to be spent, and who meant to sell each of his brothers' deaths as dearly as the Palace required.