The Halls of the Ancients supplement is an expansion to the core Necromunda game, offering players a wealth of new content to explore. The supplement introduces players to a long-abandoned city deep beneath the Underhive, filled with ancient ruins, hidden temples, and mysterious artifacts. The book provides detailed descriptions of the city's layout, factions, and plot hooks, allowing players to create their own adventures within the ancient city.

The lore of Necromunda is rich and complex, with a deep history that spans thousands of years. The world was once a thriving planet, home to advanced civilizations that possessed technology and knowledge beyond that of modern times. However, a catastrophic event known as the Overfall brought about the downfall of these civilizations, plunging the planet into a dark age. The remnants of these ancient cultures are now the stuff of legend, with many seeking to uncover their secrets and harness their power.