A Night in the Lonesome October - Egypt 1925
Once every few decades when the moon is full on the night of Halloween, the fabric of reality thins and doors may be opened between this world and the realm of the Great Old Ones. When these conditions are right, men and women with occult knowledge may gather at a specific ritual site to hold the doors closed, or to help fling them open.
Should the Closers win, then the world will remain as it is until the next turning… but should the Openers succeed, then the Great Old Ones will come to Earth, to remake the world in their own image (enslaving or slaughtering the human race in the process). The Openers have never yet won. These meetings are referred to as “The Game” or “The Great Game” by the participants, who try to keep the goings-on secret from the mundane population.