An Dương Vương and the Ou lords built the citadel Cổ Loa, literally "Old Snail"; so called because its walls were laid out in concentric rings reminiscent of a snail shell. According to legend, the construction of the citadel was halted by a group of spirits seeking to gain revenge for the son of the previous king. The spirits were led by a white chicken. A golden turtle appeared, subdued the white chicken, and protected An Dương Vương until the citadel's compleition. When the turtle departed, he left one of his claws behind, which An Dương Vương used as the trigger for his magical crossbow, the "Saintly Crossbow of the Supernaturally Luminous Golden Claw".