Post History

A "mystery cult" is an anthropological term for a religion which keeps some items of faith (and usually practice) secret, known only to those who are selectively initiated into the religion. The term originally rose to describe Greek cults which, rather than openly and generally worshipping the complete Pantheon, secretly held rituals to worship specific gods or persons raised to divine status.

There are any number of religions which have held special information for the use of the inner members, as a matter of special privilege and enlightenment. For example, the Church of Scientology is known to have the outer church, where members take classes, are audited, and eventually graduate to the status of Clear; and an inner church and a militant church (the Sea Organization) which is taught the secrets of becoming an Operating Thetan and how Xenu brought souls to Earth.

In this specific instance, the usage is much less serious: it is an analogy about the difference between "mere" players and new GMs, and experienced GMs who actively discuss the ways and means of running games.

Compare and contrast SMOFs, the Secret Masters of Fandom, who run SF conventions.