Here’s a little known story of Karna’s previous birth. The Mahabharata mentions that Karna was a demon named Dambhodbhava in his previous life. This demon had terrorized the universe on the strength of a blessing he had received from the sun-god. He had been blessed to have a thousand kavachas which had the following characteristics.
They could only be destroyed one at a time.
They could only be destroyed by someone who had performed a thousand years of austerity.
They would cause the immediate death of the destroyer of the kavacha.