The Puranic Genesis
The story begins with the *Samudra Manthan*, the churning of the cosmic ocean by gods (*Devas*) and demons (*Asuras*) to obtain the nectar of immortality. When the nectar emerged, Lord Vishnu, disguised as the enchantress Mohini, sought to distribute it only to the gods.
A clever Asura named Svarbhanu saw through the ruse, disguised himself as a god, and sat between the Sun (Surya) and Moon (Chandra) to receive a sip. They immediately exposed him, and Vishnu swiftly decapitated the Asura with his Sudarshana Chakra.
Because the nectar had passed his throat, both parts became immortal. The head, forever craving but never satisfied, became **Rahu**. The headless body, possessing experience but no senses to desire more, became **Ketu**. Filled with eternal vengeance against the Sun and Moon, they were granted the "boon" to periodically swallow them, causing eclipses.