"Tarzan and the Leopard Men" (Tarzan #18) by Edgar Rice Burroughs

As the steel-clawed Leopard Men look for victims for their savage rites, the secret cult strikes terror into the hearts of all the villagers. Only Orando of the Utengi dares to declare war on them. And with Orando goes Tarzan of the Apes—but a strangely changed Tarzan, who now believes that he is Muzimo, a spirit or demon who was Orando’s ancestor. But there are traitors among Orando’s people. And in the village of the Leopard Men is Kali Bwana, a young American woman who has come to Africa to find a missing man. Only Tarzan can save her...