What does the highest trained, indoctrinated, Tempestus Scions unit do? Well, this gives you some of the answers. If you are versed in the 40k universe then you'll fit straight in, if not, you'll so get involved with the way the unit operates, it's a story of conflict and how a cohesive unit works together to survive in the increasing difficult circumstances. With local forces resisting, what they see as interfering, outside and uncontrollable Primadonna's, and an enemy who see them as a spanner in a carefully orchestrated plan.