What is the snake motif?

Snakes appear over and over throughout the book, from the giant sacrifice of snakes in a fire to the stitching on tiger-skin garment worn by a terrifying monster guarding the Pandava camp. Throughout the book, snakes represent something dangerous yet not entirely wicked. We read stories of people getting turned into snakes or having to encounter snakes, and while there is always some trouble afoot, it's clear that these creatures are nonetheless dominated by humans.