In the ancient world, a guy captures a scrawny twelve year old amazon in the forest. The normal thing to do would be to chop off her head, preserve it as a trophy, and cook the rest of her, but he is quite far from home.

After raping her, her offers to release her, but only if she swears that she will come to his house at a predetermined later date(third winter solstice from now?) and surrender herself to him.

He tells no one. They would only berate him for trusting an amazon with an oath that even civilized people probably wouldn't keep, and wasting the opportunity. But sure enough, she arrives at his village right on time- Grown and with a toned, womanly figure- Finds him outside his house, and strips and kneels in submission.

She eagerly sleeps with him, and later freely allows him to slaughter her while everyone else in the village merrily watch. The feast that follows will be remembered for a long time.

(I think there is also potential for this world, where "civilized" people share a region with amazons and consider them fair game or even pests, while still sleeping with them and adopting the male babies they bring to their villages)