An L. Sprague de Camp collection contains the Drums of Tombalku, The People of the Black Circle, The Slithering Shadow and the Pool of the Black One:
Conan the Adventurer : The Drums of Tombalku - Robert E. Howard
Conan the Adventurer : The People of the Black Circle - Robert E. Howard
Conan the Adventurer : The Slithering Shadow - Robert E. Howard
Conan the Adventurer : The Pool of the Black One - Robert E. Howard
A story that was completed by de Camp.
Conan has been captured after the destruction of a mercenary band he was fighting in, but a friend escapes. The friend rescues a girl, and takes her back to her home city, but leaves when the horror in the Red Tower awakes, and he has to combat it.
Riding into the desert he meets Conan, who has apparently impressed his captors enough, the riders of Tombalku, that he now rides with them.
They all go to Tombalku, and Conan and Amalric briefly instruct the military there, before they fall foul of racism and a wizard, and decide to leave, post haste.
3 out of 5
Conan is again in a leadership position, and seven of his lieutenants have been captured and are under sentence of death. He goes to see what he can do about it. In a flash, he makes off with their leader, the Devi. She is not all he has to worry about, as spies, plots and the wizardry of the Black Seers will all hinder him, not to mention the odd small army, along with the Devi herself.
4.5 out of 5
Conan and the woman with him find a strange city in the desert, after attacks and problems, they finally come across two weird inhabitants, a man and a woman :
"..I am Thalis the Stygian," she replied. "Are you mad, to come here?"
"I've been thinking I must be," he growled. "By Crom, if I am sane, I'm out of place here, because these people are all maniacs."
The strange, deadly black shadows don't care who they take, though, and Conan and Natala must face those, and weird dream warriors, before the end.
4 out of 5
Conan has escaped an island where he was in trouble, and swum out to a nearby ship, boosting himself over the side and inviting himself onto the crew.
He plots to take over leadership, but when he follows the pirate leader ashore later, he gets more than he bargained for with a lot of black followers and something nasty in the Pool.
He rallies and rescues what is left of the pirate crew, and has himself a ship, and a woman.