The legend of Trọng Thủy and Mỵ Châu involves a pair of star-crossed lovers which is similar to the Romeo & Juliet archetype. Trọng Thủy was the son of Governor Triệu Đà of the Nanhai Commandery, who was originally part of the Qin Expeditionary Force sent to pacify the region, while Mỵ Châu was the daughter of the An Dương King of the kingdom of Âu Lạc. Both sides were at a stalemate of a nearly decade-long war, for although Triệu Đà was able to conquer the entire northern half of the Âu Lạc kingdom (though at great cost due to having to go against the Âu Việt tribes' guerilla warfare tactics), the An Dương King was able to defend the remaining territories and the capital, Cổ Loa, using an enchanted ballista which was able to fire thousands of arrows in a single volley, slaying thousands of men.
Eventually both fathers sued for a ceasefire and alliance, sealing the treaty by arranging a marriage between their children, Trọng Thủy and Mỵ Châu. The wedded couple, despite having been pushed into this politically motivated union, developed a deep love for each other. But Trọng Thủy, after moving to Cổ Loa, also performed espionage for his father, stealing the golden claw of the enchanted ballista and replacing it with a fake. This paved the way to the downfall of Âu Lạc and the subsequent takeover by Triệu Đà in forming a new independent kingdom of Nam Việt by 204 BC.
This legend is also used to explain the origin of the pink pearls found along the northern Vietnamese coast. In the final days of Âu Lạc, the king and Mỵ Châu attempted to flee capture by Triệu Đà's victorious forces. Not forgetting her love for her husband, Mỵ Châu left a trail of goose feathers for Trọng Thủy to be able to locate her. The An Dương King, upon discovering the cause of why the Qin pursuers were able to maintain chase, charged her with treason, and had her executed (and in some versions of the legend through decapitation). Her blood spilled into the ocean and was eaten by the oysters, which would become the pink pearls. Trọng Thủy eventually caught up but found his wife dead. He returned with the body of his wife to Cổ Loa, and soon thereafter committed suicide.