During Samundra Manthan(the churning of the ocean), Narayana aka Krishna and Nara aka Arjuna both fought with Danavas and Saved #Amrita from Demon's hand. read more
As per samudra manthan is concerned the key roles were played by Vishnu.He through his 'evil' mind( treacherous basically) made this happen at the first place through hia chaos agent Narad Muni. You can read for how. He supported the churning object mandrachit( spell maybe wrong). He became Mohini to have some ‘drooling effects'. read more
The samudra manthana is one of the best-known episodes in the Hindu mythology, narrated in the Bhagavata Purana, in the Mahabharata and in the Vishnu Purana. The samudra manthana explains the origin of amrita, the nectar of immortality. read more