The gods went to Vishnu for help after being cursed by the sage Durvasa and losing their strength. Vishnu instructed them to churn the ocean of milk to obtain amrita (nectar). When the mountain used to churn the ocean began sinking, Vishnu took the form of a giant tortoise to support the mountain on his shell. As the churning continued, various items emerged from the ocean including poison, which Vishnu helped mitigate the effects of.