Vasuki was used as the rope to churn the ocean of milk in the Hindu story of Samudra Manthana.
The devas and asuras sought amrita, the nectar of immortality, hidden in the cosmic Ocean of Milk. They used Mount Mandara as the churning rod and wrapped Vasuki, the great naga associated with Shiva, around it. The two sides alternately pulled the serpent, rotating the mountain and churning the ocean.
Mount Mandara began sinking, so Vishnu supported it in his Kurma, or tortoise, avatar. The churning produced many treasures, including Lakshmi, the divine physician Dhanvantari, and the deadly poison halahala. In several versions, fumes or poison emerged from Vasuki’s mouth, terrifying the participants; Shiva consumed the poison and became known as Nilakantha, “blue-throated.”
Vasuki is sometimes confused with Shesha or Ananta, another immense serpent closely linked with Vishnu. Shesha supports Vishnu in cosmic imagery, whereas Vasuki’s defining role in this episode is serving as the churning rope.