Khemsa is a character from Robert E. Howard's story "The People of the Black Circle". This story was first published in Weird Tales as a three-part serial in the September, October, and November issues of 1934. The story can also be found in the Ace/Lancer paperback Conan the Adventurer; the Berkley/Putnam hardbound collection, The People of the Black Circle, the Donald M. Grant Limited Edition The People of the Black Circle, and the Gnome Press collection The Sword of Conan. Marvel Comics adapted the story into comic form in The Savage Sword of Conan issues 16-19.
Khemsa is an adept of the Black Circle of Yimsha. He has risen in power almost that rivals the Master of the Black Seers. Some of Khemsa's sorcery is based on hypnotism, and relies on the subconscious priming of the locals to take control of their bodies. He is also skilled at martial arts and can break necks with a single blow. He managed to avoid even Conan's blows. He generally wears a camel-hair robe and a green turban.
Khemsa had a magical girdle made of a woman's black hair, which gave protection against certain magical effects.
In the end, Khemsa and Gitara were killed by adepts of the Black Circle after betraying them. His girdle did not protect him, presumably (according to Conan) because of his previous connection to them. Khemsa was trapped in a rockslide but survived long enough to pass the girdle to Conan and urge him to kill the Black Circle members and the Master.