“Lord Marahal Dreir” is a fabrication designed to hide the fact that one of the greatest Militarum officers of the modern age is actually a hyper-intelligent and patriotic Krieg Steed. What you see atop the steed (henceforth known as Steed Dreir) is actually one of many servitorised clones, stuffed into battledress and secured atop the real Lord Marshal. All of Dreir’s speeches are actually subvocalisations from Steed Dreir projected from a remote vox emitter within Dreir’s mask. The inherently muffled speech of Krieg soldiers helps to hide this fact. You notice how Dreir’s steed is always saved from grievous wounds and restored to health? It’s framed as Dreir respecting and admiring his mount, but it’s actually because high-ranking members of the Militarum, Inquisition and Adeptus Terra find Steed Dreir’s battle expertise, strategic mind and ability to engage Krieg’s soldiery to be invaluable. It also helps to sell the so-called “immortality” of the Lord Marshal, because if a Dreir clone is fatally wounded, they just make a new one for Steed Dreir to utilise. They’ll even let Steed Dreir eat the old clones as a means of honouring them. Steed Dreir is, despite all of the tactical and social intelligence, still a Krieg steed, and clone meat is decently nutritious.