from The King in Yellow wiki
Who are they?
Arthur Praxis, responsible for The Longevity Diet (which was on the New York Times Bestseller List for 36 weeks) and countless other fads, established the New Theologians in 1990, sharing experiences and experimentation with breathing and visualising techniques, self-hypnosis and tantric sex. On the 24th February, 1993, he attempted to add spirit-channeling to the 'routine', to contact the Overmind - inadvertantly he contacted an alien entity, which spoke through him of all number of thoughts and exhortations, in particular of the ethereal beauties of Carcosa and of The Court of The Yellow King, where all souls are welsome and every sensation is laid bare and redeiscovered. Since then Praxis has been able to channel the Voice to new audiences, all those who've come under the sway of it joining the cult, now going by the name Critical Mass Theologians.
What are their methods?
Much like Scientologists, Critical Mass Theologians appear as friendly (and relatively sound) individuals, supported by some very good PR and friends in high places, often famous ones. Praxis has an ability to channel the Voice, speaking coolly, calmly and hypnotically. Even though who don't join are touched and changed forever by the experience, effectively lending their mind to the critical mass.
What are their beliefs?
Xastur, a manifestation of some sort of alien superconsious which channels its Voice through Praxis, can only be realised fully on earth through being exposed to enough people's minds - a critical mass of humans – at which point it will be able to manifest The Court of The Yellow King here. Furthermore, the manifestation of The Court is the only way to stop the resurrection of evil entities called Xothians, who will usher in an age of destruction if not prevented.
Originally mentioned in Cthulhu Live - Lost Souls by Philip Salmon, as a sample Cult of Hastur.