While not as strongly linked with the Carcosa Mythos as the colour yellow, black has a number of associations through The King in Yellow. Most notable are the black stars that hang in the sky over Carcosa. The colour also has particular portent in some the stories:
- In the story The Yellow Sign, the eponymous Sign was inlaid in a clasp of black onyx.
- In the story The Demoiselle D'Ys, the 'black V-shaped figure' on the neck of the viper is remarked as signifying 'certain death'.
A further association of black with the Mythos is found through Nyarlathotep. See colourful beings for beings associated with the colour black. Black is also one of the two colours associated with the Black and Red Mythos.