I read this short story maybe 10-12 years ago, about an explorer who discovers or goes looking for a mysterious tribe, I think in South America or possibly Africa. There might be something about shrunken heads or they know the secret of making them. He refers to their queen as a ‘Venus’ with dark skin but classic European features. The explorer and the queen fall in love and marry, but at the wedding feast, the witch doctor curses the explorer and tells him there was poison in the goblet he drank from. The queen immediately reaches for the same goblet and drinks from it too. They agree to part so as not to have to witness the suffering of the other, and also promise not to commit suicide to end their suffering.
The story is narrated by a friend, who had only recently met the explorer, already suffering and ill from the poison, and I think the story is told to him over several nights. The friend remains as witness as the illness progresses, the explorer suffers horribly as he is slowly deformed and shrunken down to about 2-3 feet tall. He dies in agony.