It introduced the original 20 Space Marine Legions as well as their Primarchs. The book Realm of Chaos: The Lost and the Damned (Rick Priestley and Bryan Ansell, 1990) was the first book from Games Workshop to give a backstory for the Space Marines.
Space Marines were first introduced in Warhammer 40,000: Rogue Trader (1987) by Rick Priestley, which was the first edition of the tabletop game. See also: List of Warhammer 40,000 novels
