The Quest for Amrit
अमृत मंथन की कथा
Quick Answer
The quest for Amrit (nectar of immortality) drove the Devas and Asuras to churn the ocean together. After the churning, Vishnu as Mohini distributed the Amrit only to the Devas. The demon Rahu sneaked a sip but was beheaded by Vishnu's Sudarshana Chakra before he could swallow.