Hastur, also known as the Yellow King, is a fictional cosmic entity that first appeared in Ambrose Bierce's short story Haïta the Shepherd (1893) and was later expanded on by Robert W. Chambers, H.P. Lovecraft and August Derleth.
History[]
Hastur debuted in Ambrose Bierce's short story Haïta the Shepherd (1893), in which he was presented as a benevolent god of shepherds.
In Chambers' The King in Yellow (1895), a collection some of which are horror stories, the word "Hastur" is used to describe several concepts such as character and a place.
In Lovecraft's The Whisperer in Darkness (1931) mentioned Hastur alongside many other deities and locations of his own mythology, such as Cthulhu.
August Derleth, a friend of Lovecraft, turned Hastur into a Great Old One, half-brother to Cthulhu and spawn of Yog-Sothoth, who lives in Carcosa. Derleth also presented a rivalry between Hastur and Cthulhu.
The character has had influence in pop culture beyond this: a demon named Hastur appears in Neil Gaiman's and Terry Pratchett’s novel Good Omens and he served as the possible background villain in the first season of True Detective as the "Yellow King". The Yu-Gi-Oh! Trading Card Game also features a monster with the name "Old Entity Hastorr".
It is likely that Hastur is entirely fabricated by the Tuttle Cult and that they worship him in earnest, but he isn't a real entity. It is never fully revealed or explored as to whether the cultists have been in contact with an existential entity called Hastur. However, there is every possibility that he exists as a real force in the world. The strongest clue for this is the vortex vision that Rustin Cohle has at the final confrontation in Carcosa. Cohle states that he has had no visions or drug induced hallucinations in years (which is revealed in other scenes to be a lie), but suddenly has one in the presence of the shrine to Hastur. It may only be an extremely latent drug hallucination however, or one brought on by the stress of the final confrontation with Childress.
Another hint that the Yellow King was in fact a real cosmic entity in league with the cult is the apparent prescience of the cult's members. Moments before Marty impulsively executes him, Reggie Ledoux briefly spoke with Rust, saying that he had seen him in a dream, before whispering references to Carcosa, implying that Reggie knew his death was imminent somehow.