Vorax

The Ring of Iron encircles Mars like a broken halo, standing as the last contested outpost of the Dark Mechanicum inside the Imperial Fists' blockade. But those rogue priests and adepts lurking in the depths will soon face a new enemy, and the hunters shall become the prey...

Read it because
See the Vorax battle hunters in action against the traitors of the Dark Mechanicum. This Quick Read also gives an insight into the war for Mars that rages within the Solar System itself arguably the second most important battleground of the entire Heresy.