Tarzan the Invincible Edgar Rice Burroughs - Tarzan the Invincible is a novel by American writer Edgar Rice Burroughs, the fourteenth in his series of twenty-four books about the title character Tarzan. The novel was originally serialized in the magazine Blue Book from October 1930 through April 1931 as Tarzan, Guard of the Jungle.Tarzan, his monkey friend Nkima, and Chief Muviro and his faithful Waziri warriors prevent Soviet communists from looting the lost city of Opar. The story also prominently features Tarzan's lion allyJad-bal-ja.This book marks the last appearance of Opar and La in the Tarzan series, aside from the juvenile piece Tarzan and the Tarzan Twins with Jad-Bal-Ja the Golden Lion (1936), which was published later but is chronologically earlier.