'The Black Stone' is a short story by Robert E. Howard, first published in 1931, and is a classic example of cosmic horror. The story follows an unnamed narrator, an antiquarian and scholar, who becomes obsessed with an ancient monolith called the Black Stone after reading references to it in historical documents. The Black Stone is located in a remote region of Hungary, where strange and disturbing events have been associated with it for centuries. Intrigued, the narrator embarks on a journey to investigate the mysterious artifact.

Upon reaching the location, he discovers that the local villagers are deeply superstitious about the monolith, avoiding it at all costs. As the narrator spends a night near the Black Stone, he experiences a terrifying vision that reveals the dark and sinister history of the monolith, tied to ancient and monstrous gods.

The story reflects Howard's skill in blending adventure, horror, and mythology, drawing on the influence of H.P. Lovecraft's Cthulhu Mythos. 'The Black Stone' presents a chilling atmosphere and themes of human insignificance in the face of ancient, incomprehensible forces, making it a significant contribution to the genre of weird fiction.