One-line: demon pair born while Vishnu sleeps, killed only after the Goddess releases him from sleep.
First appears: Book 1, in Book 1 retelling.
Who they are: Madhu and Kaitabha are the first major demon pair in the Purana. They appear during cosmic dissolution while Vishnu is asleep and Brahma is vulnerable. The point is not just that Vishnu kills them; the point is that Vishnu cannot act until the Goddess of Sleep lets him wake.
What they do that matters:
- Threaten Brahma while Vishnu sleeps.
- Force Brahma to praise Yoga Nidra.
- Are killed by Vishnu after the Goddess withdraws from him.
Other names: None in this storybook layer.
Family / lineage (when relevant): Not central for first-time reading.