The Gasmask Gazetteer is a supplement for Unhallowed Metropolis, Revised, of interest to and use by Narrators and players alike. Each installment of the Gazetteer shines a light upon a location in the city of London, 2105 A.D. and the inhabitants thereof and relates to a specific Calling. These places are described in grim detail for use by Narrators seeking locations to include in their games of Unhallowed Metropolis and include statistics for important nonplayer characters. Further, players may find these locations and non-player characters useful in describing the backgrounds of their own characters. Finally, each installment of the Gazetteer concludes with several items intended for the use of players, including new Calling-specific Stunts as well as a number of new combat Stunts, Qualities, Impediments, or equipment of use to any character.