Queen of the Martian Catacombs: an Eric John Stark Adventure, Paperback

"Queen of the Martian Catacombs" marks the debut of one of Leigh Brackett's most iconic characters: Eric John Stark: orphan child raised on Mercury, who becomes a mercenary, fighting injustices across the solar system.
Eric John Stark is hunted by Earth police in the Martian desert. Simon Ashton is with them and makes a deal with Stark to act as his agent in preventing a holy war.
An unscrupulous ruler of a Martian Low-Canal city is partnering with a barbarian chief, Kynon, to plunder half the planet. Specialist mercenaries and criminals are coming from all over the solar system to join up.
When Stark reaches the city of Valkis, he witnesses a ritual that reveals deception at the highest levels.
The journey to the ancient ruins of Sinharat is beset with treachery and sandstorms, leading to a final confrontation with the secret masters of Mars.

This version of 'Queen of the Martian Catacombs, ' by Leigh Brackett, was originally published in Planet Stories, 1949, later expanded into 'The Secret of Sinharat'.