H. Rider Haggard 
She and Allan [EPUB ebook] 

Adventurer and trader Allan Quatermain seeks a meeting with the feared Zulu witch-doctor Zikali. He tells Allan he must seek out a great white sorceress who rules a hidden kingdom far to the north, and he charges Allan to take a message to her. He also gives Allan a necklace with a strange amulet, carved in Zikali’s own likeness. Zikali claims it has great magical powers that will protect Allan on his journey, but he must on no account take it off.