Howard Philips Lovecraft had a thing for the darkest day of the year and ever since his opus, Call of Cthulhu, was released in 1936, so has the “cultists”.
Cultists are followers of the Lovecraftian lore. People who read his stories and treat them like they were retelling of the truth. The thing about Lovecraft’s stories is that they are all based on insanity and if you really think about it, calling someone who thinks these are true insane would, in a way, prove them right. That is the genius of Lovecraft.
Cultist has also been a denomination for people who are generally fans of the stories, both those written by Lovecraft and those written in honour of him. Writers like John Carpenter and Cliff Burton took a lot of inspiration from Lovecraftian lore and made their own stories to further the mythos.
Most of this mythos takes place in the middle of the Holidays, on the darkest night of the year: The Winter Solstice.
Lovecraft’s stories often tells about the elder gods and dark creatures that lurk behind the veil we “sane” people put up, so we don’t have to deal with the reality. If you were ever to peek behind this veil and see the truth, you would either mistake what you saw for a nightmare, or go insane by the realisation that these things are actually happening. If you were to tell anyone about what you saw, they would either dismiss you for an insane person or investigate and see the truth themselves, which in turn would turn them insane as well.
In Lovecraftian lore, the apocalypse will not be slow and we will not see it coming. It will come from the darkness in the form of an ancient god, an amorphous blob or a pack of monsters and annihilate humanity in an instant.