Xaltana

Xaltana, the Witch Queen of Acheron, was a queen of the ancient empire of Acheron and a powerful sorceress. During her reign, Xaltana attempted to replace the worship of Set with the worship of a demon known only as the Demon God of Acheron. At some point she was taken over by the demon, and her subjects eventually conspired against her. Xaltana was buried alive by her rivals, the priests of Set, in a sealed tomb inside the temple that she had built to the Demon God. This temple is located in the northern mountains of Nemedia near Aquilonia and the Border Kingdom, in the region inhabited by the Sons of Acheron.

The Demon God remained dormant within Xaltana's corpse for thousands of years after her death. The demon was resurrected and set free after Conan and Prince Tarascus broke into the hidden temple in their search for the lost treasure mines of Acheron.