The Metal Monster by Abraham Merritt

In the wilds of the Trans-Himalayan region, a quartet of adventurers led by Dr. Walter T. Goodwin stumbles upon a tribe of human primitives forgotten since the age of Alexander the Great, and an awesome being of living metal commanded by the exiled Norhala. As Norhala’s guests, Goodwin and his team witness the mind-boggling marvels that are the Metal Monster’s way of life, and the unspeakable horrors it commits when Norhala takes it to war against her persecutors.