Its main deity was a sun god, called the Flaming God, to which Oparians offered human sacrifices. The male population was brutal and apelike, while women had a more human - even beautiful - appearance. These included the High Priestess La, who fell for Tarzan after his initial discovery of the land.
In the tunnels beneath the city were several chambers filled with gold and jewels. Tarzan has used more than once these reserves for his own benefit.
Philip José Farmer wrote in Tarzan Alive that by 1946 the city of Opar had been abandoned, although he does not discuss what had led to the population deserting their home. He also gives space to theories that Opar was not an Atlantean colony but a remnant of a hypothetical African empire, tentatively called Chadea. Later, in the novels Hadon of Ancient Opar and Flight to Opar, Farmer gives more details on that prehistoric empire, which is now referred to as Khokarsa and also has a bearing on the works of H. Rider Haggard.