O Rei em Amarelo é um livro de contos de Robert W. Chambers, publicado pela primeira vez em 1895:
There are 10 stories, the first four of which, "The Repairer of Reputations", "The Mask", "In the Court of the Dragon" and "The Yellow Sign", mention The King in Yellow, a forbidden play which induces despair or madness in those who read it.
A cidade de Carcosa é referenciada no jogo proibido.
The descriptions given of it make it clear that it must be located on another planet, or possibly even in another universe.
No Cthulhu Mythos ,
the King in Yellow is an Avatar of Hastur, so named because of his appearance as a thin, floating man covered in tattered yellow robes.