What I enjoyed about this story is that the authors wanted to expand on Howard's “The Vale of Lost Women”, which was never published in the author's lifetime. This era of Conan's life begins after “The Queen of the Black Coast”, with the titular hero in the jungles of Kush. It is here that he becomes the tribal chief of the Bamulas, which is outlined in “The Vale of Lost Women”. Carter and de Camp further explore that concept in the beginning of “The Castle of Terror”.
In the story's opening pages, Conan is on the run across the flat prairies of Kush. It is revealed that Conan was the Bamula tribal chief for approximately one year. But, a harsh drought occurred in the region and the tribe felt that Conan was the reason for the hardship. Ousted from power and forced into exile, Conan now finds himself with dwindling supplies and chased by lions. At dusk, Conan stumbles onto a strange scene, a crumbled Gothic-styled castle atop a stretch of dead grass. The pursuing lions stop their pursuit and refuse to go near the old house. Hoping to escape the rain, Conan goes inside.
While Conan is seeking shelter in the house, a band of Stygian slave raiders is also seeking shelter from the elements. They too go inside the cavernous house. Inside, Conan has an experience of astral projection, seeing himself outside of his body. Spiritually, he's attacked by hundreds of ghosts before awakening from his trance. At the top of a staircase, Conan witnesses the slaughter of the Stygians by a hideous hundred-headed spider-like creature. Escaping the house, Conan is forced to kill the remaining Stygian.
“The Castle of Terror” includes Conan reflecting on the old stories he heard as a child about King Kull of Atlantis, one of Robert E. Howard's other characters, the prototype for Conan. Conan recalls the stories of Serpent People inhabiting the land prior to mankind, an element that plays into the Kull mythos, including the very first sword-and-sorcery story in the US, “The Shadow Kingdom”, featuring King Kull. Additionally, the idea of natives refusing to follow Conan across a type of forbidden or sacred ground was used in Howard's “The Black Stranger”, which later was morphed into Treasure of Tranicos. But, instead of natives, “The Castle of Terror” uses lions. Arguably, the Kull short story “Skull of Silence” has comparisons as well, complete with Kull charging into a monolithic black house reportedly haunted by a cosmic horror.
This may be one of my favorite stories by Carter and de Camp. I love the eerie atmosphere and its similarity to an old Hammer Horror or Universal vampire flick. The concept of weary travelers attacked by a supernatural entity in a dark castle is sometimes overused, but in this story it works really well. The descriptions of the house, the creepy atmosphere, and the sense of urgency placed on the character to escape the lions was perfectly crafted. It's a remarkable combination and a mandatory read for fans of dark fantasy and horror.