This narrative gaming supplement for Warhammer: The Horus Heresy digs deep into the conflict on Isstvan V, when the civil war that went on to engulf the galaxy truly began. Recreate the utterly shocking initial attack of the Traitor Legions, as the Loyalists scramble to muster their defence and counter-attack with additional units, missions, and special rules. This book gives you the chance to play through one of the most momentous events of the entire conflict.

This 48-page softcover supplement contains:
- Background and lore: The story of the Dropsite Massacre, from the first reports of the Warmaster's treachery to the revelation of betrayal.
- Unit Profiles: Rules for the Master of Descent, Augur Command and Control Squad, and Hyperios Missile Tank.
- Additional rules: The Interdiction Cadre Prime Advantage and Battlefield Assets rules add extra dimensions to your games.
- Legendary scenario: The First Wave Mission lets you recreate the initial assault of the army of the Retribution Fleet as they first set foot on the black sands of Isstvan V.

You will need a copy of Warhammer: The Horus Heresy - Age of Darkness Rulebook and either Liber Hereticus: Traitor Legiones Astartes Army Book or Liber Astartes: Loyalist Legiones Astartes Army Book, all available separately, to use the contents of this book.