"The Black Stranger" is one of the stories by Robert E. Howard about Conan the Cimmerian, it was produced in the 1930s but not published in his lifetime. When the original Conan version of the story failed to find a publisher, Howard re-wrote "The Black Stranger" into a piratical Terence Vulmea story.
The original version of the story was later rewritten by L. Sprague de Camp, into a different Conan story, and published in Fantasy Magazine for February 1953. It was retitled "The Treasure of Tranicos" for book publication later the same year. Its first hardbound publication was in King Conan, published by Gnome Press, and its first paperback publication was in Conan the Usurper, published by Lancer Brooks in 1967. It was republished together with an introduction and two non-fiction pieces on the story and on Howard by de Camp and illustrations by Esteban Maroto as The Treasure of Tranicos by Ace Brooks in 1980.
Howard's original version of the story was first published in 1987 in Echoes of Valor and more recently in the collections The Conan Chronicles Volume 2: The Hour of the Dragon (Gollancz, 2001) and Conan of Cimmeria: Volume Three (1935-1936) (Del Rey Books, 2005).
The story finds Conan in the Pictish Wilderness, fleeing native warriors who are hunting him. To escape his pursuers, Conan scales a crag of rock, whereupon he sees the Picts inexplicably abandon the chase and turn back. He realizes the spot must be a taboo place to the Picts. The hill turns out to hold a treasure cave, along with the preserved bodies of the pirate Tranicos and his men. Conan's attempt to remove the treasure proves futile; a demon of mist forms, and attempts to strangle him. He barely escapes with his life, leaving the treasure undisturbed.
Coinciding with Conan's attempt at looting the treasure is the main plot of a character named Count Valenso Korzetta, a former noble of Zingara, who fled his homeland to escape a demon, whom he double crossed, to end up on the Western shores of Pictish territory. With his entourage came his niece, the Lady Belesa, and her handmaiden, Tina, among other soldiers and retainers. The Count is stunned when he learns that the pirate Black Zarona has landed on his shore, followed by the buccaneer, Strombanni. Both pirates believe that the Count set out for this deserted place in search of the legendary Treasure of Tranicos. The buccaneers are bitter enemies, and bring their feud to the Count's stronghold. During a meeting one night between the Count, Black Zarona and Strombanni, Conan surprisingly emerges from behind a drapery. All eyes are on Conan, as he dominates the room. The fellows learn from Conan that he himself has found the Treasure of Tranicos, and would be willing to share the loot with the others if they help him retrieve it. They reluctantly make a thieves pact, and agree to join Conan, knowing full well that they will kill him once the treasure is in their possession. Conan, on the other hand, had something else in mind for his companions, chiefly trapping them in the treasure room to have them killed by the demon, taking the treasure with the crews of both ships, and sailing away. Conan's scheme fails though, and the sailors find themselves trapped by Picts, who are surrounding the rocky cleft. The pirates once again declare a truce to combat a common foe. Once the pirates escape the cleft, it's a race to the Count's stronghold, with the Picts in hot pursuit. The story ends with the defeat of the Picts, the death of the Count, Strombanni and Black Zarona.
Howard's version of the story pointed toward a new piratical career for Conan; one of de Camp's major changes was to make it lead instead into the revolution that would bring the Cimmerian to the throne of Aquilonia. The Counts of Poitain arrive on the isolated shores, looking for Conan to lead them against the despotic King of Aquilonia, Numedides.