I can’t paint a good picture of an East Indian Rakshasa (feminine: Rakshasi) for you, since they all look different. Sources agree, though, that they are vaguely humanoid (though huge), extremely deformed (multiple heads, extra arms, that sort of thing, and generally unpleasant-looking (long tongues, big bellies). They appear in the Vedic texts (Pantschatantra, Mahabarata, Katha Sarit Sagara, etc) as your general sort of evil demonic foe. That kind of thing.
These bad boys (and girls) are strong, especially at night, and commit every sort of evil deed, from cannibalism, cutting off the top of people’s skulls to drink human blood out of, to eating food that’s been sneezed on (Oooh, eeeee-vil).
They all serve the demon king Ravana. Even though they are enemies, they seem to fulfill a purpose in the universe, perhaps as a test for heroes. They are very loyal to each other, and keep the vows they make. In their spare time, they live in a beautiful palace.
The few men brave enough to marry Rakshasi have found that they eventually mellow out and turn into beautiful women.
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