Ok, I’ll be honest, this book took at more effort to read than Vengeful Spirit and the only link I could see to the HH was the fact that the space marines of the X legion Iron Hands were all survivors of the Isstvan campaign when Horus effectively wrote a few legions off the records for good..
The tale is based around the surviving cruiser Veritas Ferrum lead by Captain Durun Atticus who managed to flee Isstvan with a mixed crew of Iron Hand, Salamander and Raven Guard, his aim to destroy those who turned against them.
They move in to the pandorax system in hope to ley prey to the enemy, in the process the mistress of the astropath detects a strong reading from the emperyean and it seems to be localised around Pythos. Atticus moves in and they make planet fall to find a lush green planet, but all is not what it seems. In the process of locating the origin of the warp signal, they discover that the planet is alive and after blood in various different ways.
When they eventually find the source of the warp signal the mistress of the Astropath detects an ememy flotilla in the empyrean and it is the ship and escorts that laid waste to the Iron Hands on Isstvan. Atticus plots and plans to seek his revenge.
As we move on in to the story another flotilla of rag tag ships arrives and they have civilians onboard and they want to make Pythos there home. As events start unfolding, the source of the original warp starts developing and the Iron Hands find something that’s is not natural within its bounds. The civilians are happy to lay down there life for no apparent reason and continue to die at the behest of the local flora and forna.
This progresses and as the Space Marines continue, other elements start appearing and the target of the Spacemarines is the structure. Atticus orders the Veritas Ferrum in to position to Destroy the structure. This turns the whole story as the population of civilians on Pyros turn out to be cultists that have been drawn to the planet for the final goal.
This story is of daemons and there transition in to the real world via Pythos, and about Atticus and his crews attempts to stop them. Can they, do they or at least get a message back to the general populas of the emperor to ensure they know what is coming.
As I said the book is different to the others in the HH series as it tackles the daemon aspect in great depth and their entry in to the domain of man (so to speak). It was hard going as I prefer the space marine tactical stories and the stories of the Primarchs and the attempts to assinate etc. There was far to much worship and daemon knowledge in this for me, but as a HH series follower, I had to read it.