a.k.a. Him Who Is Not To Be Named, the Unspeakable, the King in Yellow
A Great Old One of the Elder Mythos, dedicated to Decadence, Disorder, and Nihilism.
In Chapter 21, Gull had faint memories of him, thinking of him as an imprisoned being, perhaps trapped somewhere but still able to reach out and touch the world. He knew that cults dedicated to the King in Yellow exist in Golarion, and Dora thought of them as somehow being associated with decadent acts of bloodletting happening during public events of high culture (plays, operas, or the like).
In Chapter 29, Dora recalled that the Tatterman was one of his notable servants.
In Chapter 40, the party recalled that narcotics are consistently involved in the worship experience of Hastur’s followers.
In Chapter 50 (Part 1), the party saw his unholy symbol (the “Yellow Sign”) for the first time: a blackened silver oval with a yellow triskelion symbol embossed upon it; a small sphere at the center with three oddly-shaped barbed arms radiating out from it.
First Reference: Chapter 18
Other Notable References: Chapter 21, Chapter 29, Chapter 39, Chapter 40, Chapter 43, Chapter 50 (Part 1)