Tarzan and the Forbidden City

Tarzan and the Forbidden City (Edgar Rice Burroughs Authorized Library)
 
Book 20 of the Tarzan Series - Special Edition Authorized by Edgar Rice Burroughs, Inc.
 
Tarzan cared little for the fate of adventurer Brian Gregory, drawn to the legendary city of Ashair by the rumor of the Father of Diamonds, the world’s hugest gem. But to the ape-man the tie of friendship is unbreakable, and Paul d’Arnot’s pleas move him to agree to guide the expedition Gregory’s father and sister have organized for his rescue. The enigmatic Atan Thome is also obsessed with the Father of Diamonds, and has planted agents in the Gregory safari to spy out its route and sabotage its efforts. Both parties reach their goal, remote Ashair...as prisoners of its priests, doomed to die in loathsome rites.