"A square stone totem with a moon symbol painted on it."
Should be placed into one of the two square depressions near the door in the east corridor on the 2nd floor of the theater to unlock it.
Artaud Theater, 1F, east corridor near the staircase.
Silent Hill: Origins
The Moon Totem is an item obtainable in Silent Hill: Origins. It can be found inside a glass-case on the first floor in the east corridor inside Artaud Theater. It must be used along with the Sun Totem to open a door in the eastern corridor on the second floor of Artaud Theater.