In the reign of king Hung the Sixth (around 250 BC), the An army from the north invaded Van Lang (the name of the north part of present Vietnam). The king sent messengers everywhere to find someone who could drive the An invaders out.
In the village of Phu Dong lived a couple, who had been married for a long time but had no children. One morning, on the way to the rice paddy, the woman saw an unusually large footprint in the soil. Surprised, she put her foot on. Soon after this she got pregnant and later gave birth to a boy, whom they named Giong. Three years had passed, however he could neither sit up, nor could he say a word.
One day, the king's messenger came to Phu Dong. Hearing the messenger, Giong suddenly sat up and told his parents to invite the messenger in. Giong asked the messenger to return to the capital and tell the king that he needed an iron horse, an armor and an iron rod to fight the An invaders.
The king called in every blacksmith of the country to the capital. They worked days and nights and made a huge iron horse, a large armor and a long rod of iron.
At the village of Phu Dong, Giong started to eat more and more each day. He grew up very fast. When the iron horse, the armor and the rod came to Phu Dong, Giong stretched his arms, stood up, and transformed into a giant. He put on the armor, seized the rod, and quickly mounted the iron horse. The horse roared like thunders and breathed fire from its nostrils.
When he saw the enemies, Giong sped forward straight into to the An invaders. The fire from the nostrils of the iron horse burned many of them to death. Giong killed the enemies, striking them with his iron rod. When the rod broke, Giong pulled scores of bamboo trees from a nearby forest to fight the enemies.
After defeating the invaders, Giong rode his horse up the Socson Mountain, where he removed his armor and disappeared into the heaven. People called him since then the Heavenly King of Phu Dong (Phu Dong Thien Vuong). A temple in his memory can still be found not far from the place where he ascended, and every year there is a festival to honor Giong.