The Space Marine Legions of the 31st Millennium field a diverse and formidable range of genetically enhanced warriors and advanced war machines, superior to any other military force in the galaxy. As an Age of Darkness falls across the stars and the fires of rebellion rage out of control, the armies used to forge the Imperium turn upon each other in an apocalyptic civil war – the Horus Heresy.

This book is an essential guide for anyone who wants to command a Loyalist Legiones Astartes force in Warhammer: The Horus Heresy. It contains the rules you need to field the vast panoply of units available to Loyalist forces, from core squads, vehicles, and weapons shared by every Space Marine Legion to specialist rules for each of the Loyalist Legions – including Detachments, unique Wargear, signature units, and their legendary Primarchs.