Priests of Mars is a Black Library novel by Graham McNeill. It is the first book in a two-part series. It was published July 31, 2012.
Legend tells of a foolhardy expedition, led by the radical Magos Telok, which ventured out into the unknown space beyond the Halo Worlds in search of the 'Breath of the Gods' – an arcane device with the power to unmake and reshape the very stars themselves. Thousands of years later, the ambitious Lexell Kotov musters his Adeptus Mechanicus Explorator fleet and sets out to follow in mad old Telok's footsteps. With the might of the Imperial Guard and the Space Marines to augment his own forces, he searches for the hidden clues which will lead him to greatest power that the galaxy has ever known. But who knows what ancient perils may yet lie outside the Imperium and the dominion of mankind?