Robert E. Howard 
The Tower of the Elephant (Illustrated) 

t is set in the pseudo-historical Hyborian Age and concerns Conan infiltrating a perilous tower in order to steal a fabled gem from an evil sorcerer named Yara. Due to its unique insights into the Hyborian world and atypical science fiction elements, the story is considered a classic of Conan lore and is often cited by Howard scholars as one of his best tales.