Warlock by Dean Koontz

These excerpts detail a perilous journey undertaken by the Shaker Sandow, his giant assistant Mace, and his apprentice Gregor, as they accompany a military expedition of Darklands Banibaleers led by Commander Richter across the formidable Cloud Range to the east. The mission is to investigate the rival nation of Oragonia's acquisition of ancient, technologically advanced artifacts, particularly horseless vehicles and flying machines, discovered in the mysterious lands beyond the mountains. The group endures a treacherous trek marked by assassination attempts and natural disasters, revealing a plot by Oragonian agents, who are later implied to be more than human, to sabotage the mission and murder the men.