Kurma, the second avatara of Vishnu belongs to the Satya Yuga like the Matsya Avatar. Vishnu manifested in the form of a half-man half-tortoise, the lower half being a tortoise. He is normally resplendent with four arms and sat on the bottom of the ocean after the Great Flood. A mountain was placed on his back by the other gods so that they could churn the ocean and find the ancient treasures of the Vedic people.
The Devas had lost their inherent glory and power. Devraj Indra, the king of Devas once insulted the headstrong sage, Durvasa who enraged cursed him with the loss of power and prestige. Soon enough the Asuras wrecked havoc by dethroning the weak Indra and his associate deities.
The Devas feared that the Asuras would take over the whole world. Therefore, they prayed to Brahma, who suggested that they churn the Ocean of Milk in order to obtain the Nectar of Immortality. However, the Devas could not undertake the task themselves and struck a temporary truce with the demons to participate in the churning.
Clever Brihaspati, the teacher of the Devas manipulated the demons and allured them with the bright prospect of the ambrosia and abundant wealth lodged in the sea. After immense toil, the Deva-Asura group somehow uprooted the Mandar Mount to carry it to the ocean but the assignment seemed impossible so Vishnu commanded his Vahana Garuda to place it on the ocean.
The churning of the ocean commenced with Mount Mandar and Vasuki wrapped around it. Each side would hold an end of the snake and pull on it alternately causing the mountain to rotate which in turn would cause the ocean to churn. However once the mountain was put on the ocean it began to sink deep down. The mightiest of Devas and Asuras could not hold it and desperately resorted to the help of Vishnu.
Then, Vishnu incarnated in the form of Kurma to support the mountain.The upper right arm held the mace of Vishnu called Kaumodaki, symbolizing the power of knowledge which exalts the mind bequeathing immense physical and mental power. Thus the mace is also identified with Goddess Kali, the power of time, who destroys all that opposes it.
The second right hand of Kurma Avatar holds the lotus, which signifies detachment. The flower blooms in muddy water but neither water nor the dirt can mar the beauty of its petals. Vishnu delights in life’s pleasures but never gets lured by the charms of the world very much like the lotus.
There is a discus in the upper left hand of the Kurma Avatara called the Sudarshana which literally means beauteous sight. The symbol of a sharp instrument it removes all obstacles in attaining enlightenment.
The other left arm of Kurma holds the conch, symbolizing existence. When blown, the conch produces a primeval sound from which creation evolved.
Kurma Avatar, dived into the ocean, and lifted Mandar, by placing it on its robust back. The elated Devas and Asuras fervently resumed churning with the Lord helping out.
When the churning was in full swing the impurities of the ocean threw up the deadly poison, Halahala threatening to suffocate all living beings. Helpless the Devas ran to Lord Shiva who collected it in his palm and drank it. Alarmed his consort Parvati stopped it in his throat with her hands, causing the throat to turn blue. Shiva is called Nilakantha (nila[blue] kantha[throat]} due to this incidence. Various people animals and treasures emerged from the ocean .Sura the goddess and creator of wine, apsaras or divine nymphs, kaustubha the most valuable jewel in the world, ucchaishravas the divine horse, kalpavriksha the wish granting tree, kamadhenu the first cow and mother of all cows, Airavata the mount of Indra and Lakshmi the goddess of fortune and wealth.
As soon as the poison was removed, the Devas and Asuras resumed churning. Suddenly Dhanwantari, physician of the deities, emerged with the jar of nectar, conferring immortality. Devas watched the Asuras rushing to grab the nectar before everyone else. The terrified Devas appealed to Kurma for help who then revealed himself as the female avatara of Vishnu, Mohini.
The Asuras were struck by the dazzling Lord Vishnu in the enchanting form of Mohini and scrambled to enjoy her unprecedented beauty. Unaware that Lord Vishnu in the guise of an enchantress had descended with a specific purpose.
Infatuated, the Asuras gifted the jar of ambrosia to this ravishing woman and entreated her to distribute it among them. The damsel distracted the Asuras now totally under the spell of her charm. Mohini secretly served it to the Devas first and made sure that there was no nectar left for the Asuras. One asura, Rahu, suspected foul play and drank some nectar but before he could gulp it Vishnu slit his throat.
Then to the utter amazement of the Asuras, Lord Vishnu assumed his true form and they soon gathered that He had appeared before them as Mohini. They demanded of Vishnu their share of Nectar; but merely got a smile from him in return. Mounting Garuda, Lord Vishnu flew away to his realm.
The now immortal Devas easily triumphed over the Asuras having regained their original grandeur and might. On the advice of Lord Brahma Devraj Indra called for peace and returned to his domain with the Devas.
Lord Vishnu thus restored the lost glory of the righteous who sought refuge in him; and vanquished the aggressive unrighteous having no faith in him.
Lord Vishnu in this manner saved his True Devotees from dissolution so as to hand down divine knowledge and saved the Vedas from destruction to ensure Creation after the Dissolution.