Kurma is the tortoise, the second of the ten principal avatars of Vishnu, and his myth belongs to one of the grandest scenes in Hindu cosmology: the churning of the ocean of milk, the Samudra Manthana. The gods, weakened and seeking the nectar of immortality, amrita, that lay hidden in the cosmic ocean, agree to churn the sea to bring it up, using the mountain Mandara as the churning-stick and the great serpent Vasuki as the rope, with gods and demons pulling at either end. But the mountain begins to sink into the soft bed of the ocean, and so Vishnu takes the form of an enormous tortoise and dives beneath it, offering his broad back as the pivot on which Mandara can turn without sinking.
The churning that follows brings up a succession of wonders, the physician Dhanvantari rising with the pot of amrita, the goddess Lakshmi, the wish-granting cow, the moon, and, terribly, a world-threatening poison that Shiva swallows to save creation, before the nectar is at last secured. Kurma is thus the steady, hidden support that makes the whole cosmic labour possible, bearing the weight of the churning mountain unseen at the bottom of the sea. He is worshipped in this form at a small number of temples, and the tortoise remains an emblem of patient, world-supporting stability.