Another Ciaiphas Cain novel. This one, also, can only be found in print in the Ciaphas Cain: Hero of the Imperium omnibus, I think. Follows shortly after For the Emperor. And Cain is still Cain, you really doubt his word at point. Indeed, the footnotes point out several discrepancies. (It's once again an excerpt from his private memoirs, edited by another character, who also includes excerpts from other works to explain things Cain doesn't.)
Cain is still with the Valhallan regiment he was assigned to in that, and they are shipped off to an ice world, to fight orks, much to their delight. (Not so much to his, as the only one not native to an iceworld. His gallant attempts to get under cover before the orks arrive results in his being center stage at the first assault -- and because the troops about him wear camo, the only one visible. Their ambush works fairly well, but when he hears a miner complaining about the way both the Administratum and the Mechanicus people are insisting that there is nothing in the disappearances in the mines, he leads those checking it out below.
This being Cain, this is not, after all, the route to safety. It involves a desert creature where it has no business being, a tomb that ought not to be there, a warp gate, discovering the orks have found a way into the tunnels, Cain's splitting his team to get the wounded to safety, destroying a corpse so as to leave no evidence they were there, a plan to set off explosives in the mine, a Mechanicus priest delighted with the bounty found deep in the mines, and much more.