Running Masks without the Companion is like performing Hamlet with only the script but no directing notes. You can do it, but you will miss layers of depth and historical texture.
The Masks of Nyarlathotep campaign is famous for its complexity. It is a massive, globe-trotting sandbox where player characters investigate a cult conspiracy spanning several continents in the year 1925. Keeping track of hundreds of NPCs, clues, and timelines is a monumental task for any game master (Keeper). masks of nyarlathotep companion pdf