What does «GM mystery cult» mean and where does it come from?
As far as I understand, the term is sporadically used in the indie community or former Forge diaspora. I searched for it in the Forge archives, but got no hits.
What is the source of the term and is there a clear definition?
My current understanding is that it refers to the game master not being open about their methdology for running the game; whether they have a plot railroad or not, what they improvise versus have prepared, whether they fudge or not; and generally the social expectation that these are secrets the game master should keep.