On Isstvan V, the Retribution Fleet sought to bring Horus to account for the atrocities he had already committed against the Imperium. Unbeknownst to them, the roots of corruption ran deeper than any had yet dared to imagine. On the black sands of the Urgall Depression, brother opened fire on brother as the Horus Heresy began in earnest. It would come to be known as the Dropsite Massacre, and some Legions would never recover.

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 Warmasters 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 ofWarhammer: The Horus Heresy Age of Darkness Rulebookand eitherLiber Hereticus: Traitor Legiones Astartes Army BookorLiber Astartes: Loyalist Legiones Astartes Army Book, all available separately, to use the contents of this book.