Eighteen generations of Hùng Kings passed, and the nation of Văn Lang was peaceful. Đến the reign of Thục Phán, the Dragon and Fairy blood surged once more. He led his army to defeat the invading Qin forces, establishing the nation of Âu Lạc, and setting up the capital in the fertile Central Highlands, where heaven and earth harmonized, and there, the Cổ Loa Citadel was built.
One night, as the heavens raged with a storm, and lightning tore across the sky, Thục Phán was struggling by the riverbank, trying to build the walls which kept collapsing. The earth trembled, the waters surged, and amidst the silver waves, a colossal Golden Turtle (Kim Quy) emerged, its eyes bright as stars, its voice resonating like a bronze bell:
"Your Majesty, you bear the Dragon and Fairy blood, and your heart is turned towards the nation, but your will is not yet aligned with Heaven. Listen to my words this is sacred land, and can only be defended by heart and wisdom, not merely by force and blood."
Thục Phán knelt, bowing his head three times:
"If the deity takes pity on my people, please show us the way to build the citadel, so that the people of Âu Lạc may have a place of peace, no longer worrying about invaders."
Kim Quy smiled, its voice echoing like thunder:
"Take the soil where the dragon lies as the foundation, and use the direction of the phoenix's flight as the axis the walls shall be as enduring as the people's resolve. When the citadel is complete, I shall grant you an item: THE GOLDEN TURTLE CLAW, to be crafted into the Linh Quang Crossbow (Sacred Light Crossbow), one shot of which can scatter a thousand enemies."
Having spoken, Kim Quy dove into the water. Only the moonlight and a golden, brightly glowing claw remained on the river surface.
Thanks to Kim Quy's guidance, the Cổ Loa Citadel was successfully erected, its walls reaching tens of thousands of feet high, coiling three times like nine segments of a dragon, intricately surrounded by deep moats. When the sacred crossbow was finished, Kim Quy appeared once more, saying:
"Guard this turtle claw carefully, for it is not just a weapon, but the soul of the nation. If one day the person holding the crossbow allows their heart to waver, the nation will be lost, and the people scattered."
An Dương Vương clasped his hands:
"I shall engrave the deity's words in my memory."
He ordered guards to protect the crossbow, believing that with the divine artifact in hand, Âu Lạc would endure for a hundred generations. But fate had set a different wind to blow into people's hearts.
The Southern Kingdom (Âu Lạc) was powerful at that time, causing the Northern Kingdom (under Triệu Đà) to fear. King Triệu Đà then sent his son, Trọng Thủy, to sue for peace, under the guise of forging kinship, but secretly seeking an opportunity to steal the sacred crossbow's secret.
The first day Trọng Thủy stepped into the citadel, he met Princess Mỵ Châu, the King's daughter. Her eyes were like an autumn lake, clear and sorrowful. Trọng Thủy bowed his head:
"I am from the North, coming for peace and friendship, yet I fear hearts here are not amicable, seeing only the border."
Mỵ Châu replied softly:
"If you come for peace, this land and river will open its heart, just like my father. But if you come with deceit, Heaven and Earth shall record your name in blood."
Trọng Thủy bowed slightly, his voice subdued:
"I have come for both for peace and for you, My Lady."
In the following days, the two walked side by side within the Loa Citadel. Mỵ Châu believed in the man, believed in love, and on a moonlit night, she showed Trọng Thủy the sacred crossbow, the divine relic guarding the nation, thinking: "He is my husband, not an enemy."
When Triệu Đà brought his army over, An Dương Vương smiled calmly:
"The invaders have come. Just one crossbow shot, and they will scatter like dust."
But when he pulled the crossbow, the arrow would not fly. The spiritual power was lost, the crossbow broke, and the citadel walls collapsed. The invaders poured in like a flood, the people scattered. An Dương Vương was aghast. He carried his daughter onto his horse and fled towards the sea. On the way, the divine Kim Quy appeared amidst the fog, its eyes cold as ice, its voice echoing:
"The invader is right behind Your Majesty!"
The King turned back, seeing only Mỵ Châu seated behind him, her robe stained with blood, her hair disheveled. An Dương Vương gritted his teeth and shouted:
"Daughter, have you betrayed your father, betrayed the nation?"
Mỵ Châu burst into tears, her voice broken:
"Father, I only believed the man I loved, and never sold the nation. If I have erred, please let me die by my father's hand."
An Dương Vương drew his sword one swift slash, and blood sprayed. She fell, her silken robe fading red. From the distant sea, waves swelled. The divine Kim Quy spoke again:
"The fault lies not with the daughter, but with the heart that lost its clarity. Keep this lesson, and build a new nation."
An Dương Vương threw his sword into the sea and cried out:
"If the soul of the Dragon and Fairy still remains, I beg you, lead me back to the water palace, so I may atone to my ancestors."
Having spoken, he plunged into the sea. The sea closed over him, leaving only red blood drifting with the silver waves. Trọng Thủy returned, finding Mỵ Châu's body on the shore. He embraced her, sobbing uncontrollably:
"My Lady, I truly loved you, only deceitful because of the nation's command. If there is an afterlife, I vow to become the grass and trees by your grave."
Then, he threw himself into the well inside the citadel, dying beside her. Since then, the water in the well turned into tears, Mỵ Châu's blood transformed into pearls, and folklore tells that when those pearls are washed with the water from Trọng Thủy's well, they glow brightly, like pure love within sin.
The nation was lost, the people were gone, but the oath remained forever. The divine Kim Quy did not return to the sea, for it remained in the hearts of the Việt people, teaching them that the nation might be lost once, but loyalty and righteousness (lòng trung nghĩa) must be kept for eternity.