The "Halls of the Ancients" likely refers to a specific terrain set or a campaign/book focused on exploring ancient ruins, which are a staple of the Necromunda setting. Such materials usually provide gamers with detailed terrain pieces to build and paint, as well as narrative-driven content that can be used to create immersive gaming experiences.
Every turn, the Arbitrator rolls a D66 (two six-sided dice) on the Whispers Table. Results range from "False Echo" (no effect) to "Memory Flood" (all fighters must pass an Initiative test or be stunned as the history of the Ancients overloads their senses). necromunda+halls+of+the+ancientspdf+full
Halls of the Ancients transforms the Ironhead Squats from a solid but basic gang into a formidable force. For the first time, players can field a without constantly cross-referencing other books. The "Halls of the Ancients" likely refers to