I believe “The Lunar Cult” is adapted from a story called “The Thuggees,” which appeared in newspapers from August 22, 1949 to February 25, 1950. As Thuggees were an Indian murder cult there was probably some sensitivity toward the original title. There is internal evidence in some speech balloons that something (presumably “Thuggee”) has been whited out and replaced by the world “Lunar.”
The Phantom’s territory was a mix of India and Africa. There is more on that subject in a link below the 16-page story. For more about Thuggee go here.
UPDATE: On February 5 our friend J D LaRue furnished us with information that the story is not from the Thuggee continuity, but instead from “The Crescent Cult,” published as Sunday strips from April 10, 1955 to August 7, 1955. Thanks, J D, for the information. As J D pointed out, there are many Muslims in India, so the change from Crescent to Lunar was done in response to cultural and religious sensitivies.
As promised, more on the blurring of India and Africa in the Phantom. Just click on the thumbnail.