Kurma
In Hinduism, Kurma (Sanskrit: कूर्म; Kūrma, lit. turtle) was the second Avatar of Vishnu, succeeding Matsya and preceding Varaha. Like Matsya, this incarnation also occurred in Satya Yuga. The temples dedicated to Kurma are located in Kurmai, Chittoor district, Andhra Pradesh, and Srikurmam, Andhra Pradesh.
Samudramanthan (The Churning of The Ocean)
Purana scripture indicates that the sage Durvasa had given a garland to Indra, the king of Gods. Indra placed the garland around his elephant, but the animal trampled it, insulting the sage. Durvasa then cursed the gods to lose their immortality, strength, and divine powers. After losing the kingdom of heaven, they approached Vishnu for help.
He advised that they had to drink the nectar of immortality to regain their glory. To obtain it, they needed to churn the ocean of milk, a body of water so large they needed Mount Mandara as the churning staff, and the serpent Vasuki as the churning rope. The Devas were not strong enough to churn on their own, and declared peace with their foes, the Asuras, to enlist their help.